Elementary School Math Quiz: Understanding Tens
20 questions · exam conditions
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Understanding TensQuestion 1 of 20

Sofia has 10 pennies. They are the same as 1 dime. 10 ones equals   ten.

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Elementary School Math Quiz

Elementary School Math Quiz: Understanding Tens

Practice Understanding Tens in Elementary School Math with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Understanding Tens, giving you a quick way to practice the rules, question types, and explanations that matter most for Elementary School Math.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Sofia has 10 pennies. They are the same as 1 dime. 10 ones equals   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: This question is all about grouping in our number system. Whenever you count objects, once you gather 10 of something small, you can bundle them into 1 of the next bigger unit. That's the heart of place value. Look at the clue the problem gives you: 10 pennies are the same as 1 dime. This is exactly like ones and tens! Just as 10 pennies bundle into 1 dime, 10 ones bundle into 1 ten. So 10 ones = 1 ten. That makes 1 the correct answer. Now let's see why the others don't work. Choosing 0 would mean 10 ones make no tens at all — but you clearly have enough to make one full group of ten, so it can't be zero. Choosing 2 would mean 10 ones make two tens, but two tens would be 20 ones, and you only have 10. Choosing 10 confuses the number of ones with the number of tens — you have 10 ones, but they only build 1 ten, not 10 tens (that would be 100!). A handy way to remember: 10 ones = 1 ten, just like 10 pennies = 1 dime. Whenever you collect exactly 10 small units, you trade them for 1 of the next unit up. Watch out for the trap of repeating the number 10 as your answer — the question is asking how many tens you can make, not how many ones you started with.

Question 2

Look at 10 straws with a rubber band. What is it?​

  1. one one
  2. one ten (correct answer)
  3. two tens
  4. ten tens
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The stimulus shows 10 straws with a rubber band, representing a bundled group. Choice B is correct because the bundled group of 10 ones is called 'one ten.' Choice A is a common error where students think it remains 'one one'; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 3

Maya bundles 10 sticks with a rubber band. What is it called?

  1. one ten (correct answer)
  2. ten tens
  3. ten ones
  4. one one
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. The scenario describes Maya bundling 10 sticks with a rubber band, representing the grouping of 10 ones into one ten. Choice A is correct because the bundled group of 10 ones is called 'one ten.' Choice B is a common error where students believe bundling creates ten tens, confusing the unit; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 4

Look at 10 cubes. 10 ones is the same as   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: Whenever you see a question about "ones" and "tens," picture your place-value blocks. A one is a single little cube, and a ten is a group of exactly 10 ones bundled together into one long rod. This is all about learning how we trade small units for bigger ones. Here you have 10 cubes, and each cube is one "one." When you gather 10 ones together, they make exactly one group of ten. So 10 ones is the same as 1 ten. That's why the answer is 1 — you bundled your 10 single cubes into a single ten-stick. Now look at the traps. Choosing 0 would mean your 10 cubes make no tens at all, but 10 is enough to make a group — so this is wrong. Choosing 2 would mean you had 20 ones (two full groups of ten), but you only have 10 cubes, not 20, so there aren't enough for 2 tens. Choosing 10 is the tempting trick: you see the number 10 in the question and grab it, but 10 is how many ones you have, not how many tens. Ten ones equal only 1 ten, not 10 tens (which would be 100 cubes!). A helpful way to remember: 10 ones always trade for 1 ten, just like trading 10 pennies for 1 dime. Whenever you count 10 single things, wrap them up into one bigger group.

Question 5

Maya bundles 10 sticks. What is it called?

  1. one ten (correct answer)
  2. ten tens
  3. one one
  4. two tens
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. The scenario describes Maya bundling 10 sticks together, representing grouping 10 ones into one unit. Choice A is correct because the bundled group of 10 sticks is called 'one ten.' Choice B is a common error where students believe 10 ones equal ten tens, confusing the terminology; this happens because the concept of grouping is abstract and requires concrete experiences. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 6

Sofia bundles 10 sticks. What is it called?​

  1. one ten (correct answer)
  2. ten tens
  3. one one
  4. ten ones
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario describes Sofia bundling 10 sticks together. Choice A is correct because the bundled group of 10 ones is called 'one ten.' Choice B is a common error where students believe bundling creates ten tens instead of one ten; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 7

Look at 1 ten rod. It equals how many ones?

  1. 1
  2. 20
  3. 2
  4. 10 (correct answer)
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The stimulus shows 1 ten rod, and the question asks how many ones it equals. Choice D is correct because 1 ten equals 10 ones, showing the equivalence. Choice A is a common error where students think 1 ten equals 1 one; this happens because understanding that grouping doesn't change quantity requires concrete experiences. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 8

Look at 10 straws with a rubber band. What is it?

  1. one one
  2. one ten (correct answer)
  3. two tens
  4. ten tens
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The stimulus shows 10 straws with a rubber band, representing a bundled group. Choice B is correct because the bundled group of 10 ones is called 'one ten.' Choice A is a common error where students think it remains 'one one'; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 9

Look at 10 dots circled together. How many tens?

  1. 10
  2. 1 (correct answer)
  3. 2
  4. 0
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—1010 ones and 11 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The stimulus shows 10 dots circled together, representing a group of 10. Choice B is correct because the circled group of 10 ones is 1 ten. Choice A is a common error where students think the group represents 10 tens instead of 1 ten; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 1010 ones = 11 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 10

Jamal groups 10 counters. How many tens is that?

  1. 2
  2. 1 (correct answer)
  3. 10
  4. 5
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. The scenario describes Jamal grouping 10 counters, which forms one bundled ten. Choice B is correct because grouping 10 counters equals 1 ten. Choice C is a common error where students think the number of ones directly equals the number of tens; this happens because understanding grouping requires concrete experiences. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 11

Look at 10 unit cubes. They make how many tens?

  1. 10
  2. 2
  3. 1 (correct answer)
  4. 0
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. The scenario involves looking at 10 separate unit cubes, which represent 10 ones that can be grouped. Choice C is correct because 10 unit cubes bundled together equal 1 ten. Choice A is a common error where students think 10 ones equal 10 tens, confusing the units; this happens because place value is abstract and challenging for young learners. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones =1= 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 12

Look at 10 dots circled as one group. How many tens are shown?

  1. 10
  2. 1 (correct answer)
  3. 0
  4. 2
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. The stimulus shows 10 dots circled as one group, representing 10 ones bundled into one ten. Choice B is correct because the grouped 10 ones equal 1 ten. Choice A is a common error where students think the 10 ones mean 10 tens, confusing the units; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones=1 ten10 \text{ ones} = 1 \text{ ten}; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 13

Jamal has 10 ones. Are they the same as 1 ten?

  1. Yes, same amount (correct answer)
  2. No, 10 ones is more
  3. No, 1 ten is more
  4. No, they make 11
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario involves Jamal having 10 ones and comparing them to 1 ten. Choice A is correct because 10 ones and 1 ten represent the same quantity. Choice D is a common error where students add 10 ones and 1 ten to get 11 instead of understanding they're the same; this happens because place value is abstract and challenging. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 14

A full ten-frame (all 10 spaces filled) shows   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: A ten-frame is a special tool with exactly 10 spaces arranged in two rows of five. Whenever you see a ten-frame question, remember that the whole frame is built to help you think in groups of ten. So the key idea here is: what does a completely filled ten-frame represent? When all 10 spaces are filled, you have 10 ones grouped together. And 10 ones make exactly 1 ten. That's the whole point of the ten-frame — it bundles single dots into one neat group of ten. So a full ten-frame shows 1 ten. The choice "0" would mean the frame is empty with nothing filled in, but here every space has a counter, so it can't be zero. The choice "2" would mean you'd need two full ten-frames (20 filled spaces), but a single frame only holds 10, so there's only one group. The choice "10" is a tempting trap — it's true that you filled in 10 dots, but the question asks how many tens you made, not how many ones. Ten single dots equal just one group of ten. The trick to remember: a ten-frame counts ones until it's full, and then that full frame becomes 1 ten. Watch the wording carefully — "how many tens?" is asking about groups, while "how many?" would be asking about single counters. Ten ones always bundle into one ten.

Question 15

Emma trades 10 ones. How many tens does she get?

  1. 0
  2. 2
  3. 1 (correct answer)
  4. 10
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario describes Emma trading 10 ones for tens. Choice C is correct because exchanging 10 ones gets you 1 ten. Choice D is a common error where students confuse the units and think it equals 10 tens; this happens because place value is abstract and challenging. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 16

10 dots are circled together as one group. How many tens do they make?

  1. 10
  2. 1 (correct answer)
  3. 2
  4. 0
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS 1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The 10 dots form one group of 10. Choice B is correct because the circled group of 10 ones is 1 ten. Choice A is a common error where students think the group represents 10 tens instead of 1 ten; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 17

Look at a full ten-frame. It shows   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: When you work with a ten-frame, you're learning one of the most important ideas in early math: how small parts group together to make bigger units. A ten-frame is a rectangle with 10 boxes—two rows of 5. When every single box is filled, you have 10 counters all together, and those 10 ones combine to form exactly one group of ten. So a full ten-frame shows 1 ten. That's the answer, because "one ten" is just another way of saying "10 ones grouped together." Counting tens, not ones, is the key here—the question is asking how many groups of ten you can see. Now let's look at why the other choices don't fit. Saying it shows 0 tens would mean the frame is empty, but a full frame clearly has counters in it, so it can't be zero. Saying 2 tens would mean you'd need two full ten-frames (20 counters), but you only have one filled frame here. And 10 is a tempting trap: there are 10 counters, but the question asks how many tens, not how many ones. Ten single counters make just one ten. A helpful tip: whenever a question asks "how many tens?", pause and ask yourself, "Am I counting the little pieces, or am I counting the groups?" A full ten-frame always equals 1 ten and 0 ones. Remembering that 10 ones = 1 ten will help you as you move on to bigger numbers like 20, 30, and beyond.

Question 18

Look at 10 cubes. They are grouped into 1 ten. 10 ones is the same as   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: When you're learning about place value, the big idea is that we can bundle small units into bigger groups. A "ten" is simply a group made from 10 single cubes, or 10 "ones." Think of it like gathering 10 loose pencils and wrapping them into 1 bundle — the bundle is still the same amount, just grouped differently. In this question, you start with 10 cubes (10 ones), and they get grouped together into 1 group. So 10 ones = 1 ten. That's why the answer is 1 ten. Now let's check the others. Saying 10 ones equals 0 tens would mean the cubes disappeared or that a full group of ten doesn't count as a ten at all — but you clearly have a group, so it's not zero. Saying it equals 2 tens would mean you had 20 cubes, since 2 tens is 2 × 10 = 20; you only have 10, so that's too many. Saying it equals 10 tens would mean you had 100 cubes, because 10 tens is 10 × 10 = 100 — that's way more than the 10 you started with. That choice mixes up the number 10 with the group it forms. A helpful trick to remember: 10 ones always make exactly 1 ten. Whenever you count up 10 single things, you can trade them for one single bundle. Watch out for questions that repeat the number "10" to tempt you — the group you make is always just 1 ten.

Question 19

Jamal has 10 ones. Are they the same as 1 ten?​

  1. Yes, same amount (correct answer)
  2. No, 10 ones is more
  3. No, 1 ten is more
  4. No, they make 11
Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario involves Jamal having 10 ones and comparing them to 1 ten. Choice A is correct because 10 ones and 1 ten represent the same quantity. Choice D is a common error where students add 10 ones and 1 ten to get 11 instead of understanding they're the same; this happens because place value is abstract and challenging. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 20

Emma counts 10 ones. She groups them. Now she has   ten.

  1. 0
  2. 1 (correct answer)
  3. 2
  4. 10
Explanation: Whenever you see a question about grouping ones, remember the big idea of place value: a ten is just a bundle of 10 ones packed together. When you gather 10 single things and group them, they become one single group called a ten. So when Emma counts 10 ones and groups them, all 10 of those ones fit together into exactly 1 ten. That's why the answer is 1. Think of it like a bundle of 10 sticks tied with a rubber band — 10 loose sticks become 1 bundle. Now let's look at why the other choices don't work. The answer 0 would mean she has no tens at all, but she has enough ones to make a group, so she definitely has more than zero. The answer 2 is too many — you'd need 20 ones to make 2 tens, and Emma only has 10. The answer 10 is a trap: it's the number of ones she started with, not the number of tens she made. It's easy to just repeat the number you saw, but grouping changes what you're counting — you go from counting ones to counting tens. A helpful way to remember this: 10 ones always make 1 ten. Whenever a problem says "group 10 ones," picture squishing them into one neat bundle. The next time you see 20 ones, you'll know that makes 2 tens, and 30 ones makes 3 tens — the pattern grows by one ten for every ten ones.