This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 3×60: Think of 60 as 6 tens. Multiply 3×6=18, then multiply by 10 to get 180 (or think: 18 tens = 180). In this problem, Noah runs 3 days, 60 minutes each day. This represents the multiplication 3×60. Choice A is correct because 3×60=180 using the pattern (3×6=18, then ×10=180) or place value (3×6 tens = 18 tens = 180). This demonstrates understanding of multiplying by multiples of 10. Choice D is incorrect because it shows only 3×6=18 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 3×6=18, then 3×60=180). Use place value language (3×60 = 3×6 tens = 18 tens = 180). Model with base-10 blocks (3 groups of 6 tens rods).

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 4×90: Think of 90 as 9 tens. Multiply 4×9=36, then multiply by 10 to get 360 (or think: 36 tens = 360). In this problem, Leo has 4 boxes with 90 crayons each. This represents the multiplication 4×90. Choice B is correct because 4×90=360 using the pattern (4×9=36, then ×10=360) or place value (4×9 tens = 36 tens = 360). This demonstrates understanding of multiplying by multiples of 10. Choice C is incorrect because it shows only 4×9=36 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 4×9=36, then 4×90=360). Use place value language (4×90 = 4×9 tens = 36 tens = 360). Model with base-10 blocks (4 groups of 9 tens rods).

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 5×80: Think of 80 as 8 tens. Multiply 5×8=40, then multiply by 10 to get 400 (or think: 40 tens = 400). Another way: 5×80 means 5 groups of 80, which is the same as 5 groups of 8 tens = 40 tens = 400. The pattern is: if 5×8=40, then 5×80=400 (one more zero because 80 has one zero). In this problem, Mina has 5 boxes with 80 crayons each. This represents the multiplication 5×80. Choice C is correct because 5×80=400 using the pattern (5×8=40, then ×10=400) or place value (5×8 tens = 40 tens = 400). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it added 5+80=85 instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, if 9×7=63, then 9×70 means multiply 63 by 10 to get 630. Another way: 9×70 means 9 groups of 70, which is the same as 9 groups of 7 tens = 63 tens = 630. In this problem, students use the pattern: if 9×7=63, what is 9×70? This represents extending a basic fact to multiply by a multiple of 10. Choice C is correct because 9×70=630 using the pattern (9×7=63, then ×10=630) or place value (9×7 tens = 63 tens = 630). This demonstrates understanding of multiplying by multiples of 10. Choice B is incorrect because it shows only 9×7=63 without multiplying by 10. This error occurs when students don't understand the relationship between basic facts and multiples of 10. To help students multiply by multiples of 10: Connect to basic facts (if you know 9×7=63, then 9×70=630). Use place value language (9×70 = 9×7 tens = 63 tens = 630). Teach: multiply the digits, then add one zero.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 7×10: This is a special case where we multiply directly by 10, so 7×10=70. Another way: 7×10 means 7 groups of 10, which equals 70. In this problem, Ava has 7 bags with 10 marbles each. This represents the multiplication 7×10. Choice B is correct because 7×10=70, which is the basic pattern for multiplying by 10. This demonstrates understanding of multiplying by multiples of 10. Choice C is incorrect because it shows only 7 without multiplying by 10. This error occurs when students forget to perform the multiplication operation. To help students multiply by multiples of 10: Connect to basic facts (7×1=7, so 7×10=70). Use place value language (7×10 = 7 tens = 70). Model with base-10 blocks (7 tens rods). Practice skip counting by 10s: 10, 20, 30, 40, 50, 60, 70.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 7×10: Think of 10 as 1 ten. Multiply 7×1=7, then multiply by 10 to get 70 (or think: 7 tens = 70). Another way: 7×10 means 7 groups of 10, which is the same as 7 groups of 1 ten = 7 tens = 70. The pattern is: if 7×1=7, then 7×10=70 (one more zero because 10 has one zero). In this problem, a number line shows 7 jumps of 10. This represents the multiplication 7×10. Choice C is correct because 7×10=70 using the pattern (7×1=7, then ×10=70) or place value (7×1 ten = 7 tens = 70). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it added 7+10=17 instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

First group: $$7 \times 40 = 280$$ students. Second group: $$3 \times 40 = 120$$ students. Total: $$280 + 120 = 400$$ students. Choice A shows only the first group, choice C shows $$8 \times 40$$, and choice D shows only the second group.

Pages read per day: 9 pages. Words per page: 20 words. Words per day: $$9 \times 20 = 180$$ words. Total words after 3 days: $$180 \times 3 = 540$$ words. Choice A shows pages only, choice B shows words per day only, and choice D shows words on 3 pages.

Only the full shelves contain books. Books on full shelves: $$4 \times 80 = 320$$ books. Empty shelves contribute 0 books. Total books: $$320 + 0 = 320$$ books. Choice A shows $$7 \times 80$$, choice B shows $$3 \times 80$$, and choice D shows just one shelf.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 5×80: Think of 80 as 8 tens. Multiply 5×8=40, then multiply by 10 to get 400 (or think: 40 tens = 400). In this problem, students find 5 groups of 8 tens using place value. This represents the multiplication 5×80. Choice A is correct because 5×80=400 using the pattern (5×8=40, then ×10=400) or place value (5×8 tens = 40 tens = 400). This demonstrates understanding of multiplying by multiples of 10. Choice B is incorrect because it shows only 5×8=40 and forgot to multiply by 10. This error occurs when students don't complete the place value reasoning. To help students multiply by multiples of 10: Connect to basic facts (if you know 5×8=40, then 5×80=400). Use place value language (5×80 = 5×8 tens = 40 tens = 400). Model with base-10 blocks (5 groups of 8 tens rods).