Divide Whole Numbers by Unit Fractions

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5th Grade Math › Divide Whole Numbers by Unit Fractions

Questions 1 - 10
1

A restaurant serves soup in bowls that each hold $$\frac{1}{6}$$ gallon. On Monday, they served $$14$$ gallons of soup total. On Tuesday, they served $$16$$ gallons. How many more bowls of soup did they serve on Tuesday than on Monday?

$$12$$ more bowls served

$$10$$ more bowls served

$$16$$ more bowls served

$$14$$ more bowls served

Explanation

Monday bowls: $$14 \div \frac{1}{6} = 14 \times 6 = 84$$ bowls. Tuesday bowls: $$16 \div \frac{1}{6} = 16 \times 6 = 96$$ bowls. Difference: $$96 - 84 = 12$$ more bowls on Tuesday. Choice A uses $$(16-14) \times 5$$ instead of 6. Choice C uses the Monday gallon amount. Choice D uses the Tuesday gallon amount.

2

A carpenter needs to drill holes every $$\frac{1}{4}$$ foot along the edge of a $$7$$-foot board. He starts drilling $$\frac{1}{4}$$ foot from one end and stops $$\frac{1}{4}$$ foot before the other end. How many holes will he drill?

$$26$$ holes total

$$25$$ holes total

$$27$$ holes total

$$28$$ holes total

Explanation

When you encounter problems about spacing objects at regular intervals, you need to carefully track the actual drilling space and understand that the number of holes differs from the number of intervals.

First, let's find the actual length where holes will be drilled. The carpenter starts $$\frac{1}{4}$$ foot from one end and stops $$\frac{1}{4}$$ foot before the other end, so he removes $$\frac{1}{4} + \frac{1}{4} = \frac{1}{2}$$ foot from the total length. The drilling space is $$7 - \frac{1}{2} = 6\frac{1}{2}$$ feet.

Since holes are drilled every $$\frac{1}{4}$$ foot, you divide the drilling space by the interval: $$6\frac{1}{2} \div \frac{1}{4} = \frac{13}{2} \div \frac{1}{4} = \frac{13}{2} \times \frac{4}{1} = 26$$. This gives you 26 intervals, but here's the key insight: if you have 26 intervals, you need 27 holes because the first hole creates the starting point for all intervals.

Answer D ($$27$$ holes) is correct. Answer B ($$26$$ holes) represents the common mistake of counting intervals instead of holes. Answer A ($$25$$ holes) likely comes from miscalculating the drilling space or making errors with fraction arithmetic. Answer C ($$28$$ holes) might result from incorrectly including the excluded end spaces in your calculations.

Remember this pattern: when objects are placed at regular intervals along a line, the number of objects always equals the number of intervals plus one. Think of fence posts—if you need 10 sections of fence, you need 11 posts.

3

A art teacher is cutting construction paper for a project. She cuts $$24$$ sheets into strips that are each $$\frac{1}{8}$$ of a sheet wide. Then she realizes she needs $$50$$ fewer strips for the actual project. How many strips will she actually use?

$$142$$ strips used

$$150$$ strips used

$$192$$ strips used

$$242$$ strips used

Explanation

Total strips cut: $$24 \div \frac{1}{8} = 24 \times 8 = 192$$ strips. Strips actually needed: $$192 - 50 = 142$$ strips. Choice B incorrectly calculates $$24 \times 8 - 50 + 8$$. Choice C gives the total strips cut before adjustment. Choice D incorrectly adds 50 instead of subtracting.

4

Maya is making friendship bracelets. She has $$12$$ yards of string and wants to cut it into pieces that are each $$\frac{1}{4}$$ yard long. After cutting all the pieces, she realizes she needs $$6$$ more pieces of the same length for additional bracelets. How many total pieces will she have when she's done?

$$60$$ pieces

$$54$$ pieces

$$48$$ pieces

$$42$$ pieces

Explanation

First, find how many pieces Maya gets from 12 yards: $$12 \div \frac{1}{4} = 12 \times 4 = 48$$ pieces. Then add the 6 additional pieces she needs: $$48 + 6 = 54$$ pieces total. Choice A incorrectly subtracts 6 instead of adding. Choice B gives only the pieces from the original string. Choice D incorrectly calculates $$12 \times 5$$ instead of the two-step process.

5

A construction worker needs to mark spots every $$\frac{1}{6}$$ meter along a $$15$$-meter beam. If he starts marking at the very beginning of the beam (at the 0-meter mark), how many marks will he make in total?

$$91$$ marks total

$$89$$ marks total

$$90$$ marks total

$$92$$ marks total

Explanation

When you encounter problems about marking or placing objects at regular intervals along a length, you need to carefully consider whether you're counting the intervals or the marks themselves.

Let's work through this step by step. The worker marks every $$\frac{1}{6}$$ meter along a 15-meter beam, starting at the 0-meter mark. First, find how many intervals of $$\frac{1}{6}$$ meter fit into 15 meters: $$15 \div \frac{1}{6} = 15 \times 6 = 90$$ intervals.

Here's the key insight: if there are 90 intervals, there are 91 marks total. Think of it like fence posts – if you have 10 sections of fence, you need 11 posts. The marks occur at positions 0, $$\frac{1}{6}$$, $$\frac{2}{6}$$, $$\frac{3}{6}$$, and so on, all the way to position 15 (which is $$\frac{90}{6}$$). That's 91 positions total.

Choice A (89 marks) likely comes from miscalculating the division or subtracting incorrectly. Choice B (90 marks) is the classic trap – this is the number of intervals, not marks. Many students forget to add the starting mark. Choice C (92 marks) might result from adding both a starting and ending mark when the ending mark is already included in the count.

Remember this pattern: when marking at regular intervals including both endpoints, the number of marks always equals the number of intervals plus one. Always ask yourself whether you're counting the spaces between marks or the marks themselves.

6

Tommy is cutting ribbon for a craft project. He cuts a $$20$$-inch piece of ribbon into smaller pieces, each $$\frac{1}{5}$$ inch long. His sister cuts a $$16$$-inch piece into pieces that are each $$\frac{1}{4}$$ inch long. How many more pieces does Tommy have than his sister?

$$52$$ more pieces

$$28$$ more pieces

$$44$$ more pieces

$$36$$ more pieces

Explanation

Tommy's pieces: $$20 \div \frac{1}{5} = 20 \times 5 = 100$$ pieces. Sister's pieces: $$16 \div \frac{1}{4} = 16 \times 4 = 64$$ pieces. Difference: $$100 - 64 = 36$$ more pieces. Choice A uses incorrect calculation $$20 \times 4 - 16 \times 5$$. Choice C adds the totals instead of finding the difference. Choice D uses $$20 \times 4 - 16 \times 2$$.

7

A classroom has 6 yards of string for a project. The teacher is deciding between cutting pieces that are each $\tfrac{1}{2}$ yard long or pieces that are each $\tfrac{1}{3}$ yard long. Dividing by a unit fraction asks how many of those fractional pieces fit into 6 yards. Which claim is incorrect?

Because $\tfrac{1}{3}$ is smaller than $\tfrac{1}{2}$, $6 \div \tfrac{1}{3}$ will be smaller than $6 \div \tfrac{1}{2}$.

$6 \div \tfrac{1}{3}$ counts how many one-third-yard pieces fit into 6 yards.

$6 \div \tfrac{1}{2}$ counts how many half-yard pieces fit into 6 yards.

More pieces are made with $\tfrac{1}{3}$-yard pieces than with $\tfrac{1}{2}$-yard pieces.

Explanation

Dividing a whole number by a unit fraction measures how many fractional pieces fit into the total yards. Comparing 6 divided by 1/2 or 1/3 determines pieces for each size. For 1/2, it's 12; for 1/3, 18. Model with strings divided accordingly, showing more smaller pieces. The incorrect claim is that smaller fractions give smaller quotients, but actually larger. Generally, larger denominators enlarge quotients. Thus, 1/3 yields more than 1/2.

8

A baker has 4 cups of flour. One muffin recipe uses $\tfrac{1}{2}$ cup of flour. Dividing by a unit fraction asks how many $\tfrac{1}{2}$-cup groups fit into 4 cups. If you draw 4 cups as 8 half-cup blocks, what does the quotient of $4 \div \tfrac{1}{2}$ represent?

Half of 4 cups of flour

The number of $\tfrac{1}{2}$-cup groups that fit into 4 cups

The number of cups in $\tfrac{1}{2}$ cup

The amount of flour left after using $\tfrac{1}{2}$ cup one time

Explanation

Dividing a whole number by a unit fraction measures how many of those fractional amounts fit into the whole number. In the baker's scenario with 4 cups of flour and each muffin using 1/2 cup, this division determines how many muffins can be made. Counting the fractional units involves seeing 4 cups as 8 half-cups, so the quotient is 8. Connect this to a model like drawing 4 whole cups divided into halves, visually grouping them into 8 parts. One misconception is confusing this with finding half of the whole, but it's actually counting how many halves are there. Generally, smaller unit fractions mean more units fit, resulting in larger quotients. Thus, dividing by 1/2 yields twice as many units as the whole number itself.

9

A baker has 5 cups of flour. Each batch of muffins needs $\tfrac{1}{5}$ cup of flour. Dividing by a unit fraction asks how many $\tfrac{1}{5}$-cup batches fit into 5 cups. Which claim about $5 \div \tfrac{1}{5}$ is incorrect?

The quotient tells how many $\tfrac{1}{5}$-cup batches can be made from 5 cups.

The quotient counts how many times $\tfrac{1}{5}$ cup fits into 5 cups.

You can think of 5 cups as 25 fifth-cups, so the quotient counts those groups.

The quotient must be less than 5 because division always makes numbers smaller.

Explanation

Dividing a whole number by a unit fraction measures how many of those fractional parts can fit into the whole number. For the baker with 5 cups of flour needing 1/5 cup per batch, 5 ÷ 1/5 calculates the number of batches. We count the fractional units by multiplying 5 by 5, resulting in 25 batches. Model this with 5 whole cups each split into 5 fifths, totaling 25 units. A misconception is believing division always yields a smaller number, but dividing by a fraction less than 1 actually increases it. In general, smaller unit fractions yield larger quotients as they divide the whole into more parts. For instance, dividing 5 by 1/6 gives about 30, larger than dividing by 1/5 which gives 25.

10

A music teacher has 5 minutes to practice clapping patterns. Each pattern takes $\tfrac{1}{4}$ minute. Dividing by a unit fraction asks how many $\tfrac{1}{4}$-minute patterns fit into 5 minutes. Which statement best interprets the quotient of $5 \div \tfrac{1}{4}$?

It tells what one-fourth of 5 minutes is.

It tells how many one-fourth-minute patterns can fit into 5 minutes.

It tells how many groups of 5 minutes fit into one-fourth of a minute.

It tells how many minutes are in one-fourth of a minute.

Explanation

Dividing a whole number by a unit fraction measures how many of those short durations fit into the practice time. For 5 minutes with patterns taking 1/4 minute each, it calculates the number of patterns. Counting the units: 5 minutes equal 20 quarter-minutes. A model is a clock face or line divided into quarters, showing 20 segments in 5 units. Misconception: confusing it with finding one-fourth of the whole, but it's counting quarters. In general, smaller fractions mean larger quotients. Dividing by 1/4 quadruples the whole number.

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