Fraction Multiplication/Division

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ISEE Middle Level: Mathematics Achievement › Fraction Multiplication/Division

Questions 1 - 10
1

Liam and Chloe painted a fence that is 72 feet long. Liam painted \(\frac{3}{8}\) of the fence. Chloe painted \(\frac{1}{3}\) of the remaining portion of the fence. How many more feet of fence did Liam paint than Chloe?

27 feet

12 feet

15 feet

3 feet

Explanation

First, calculate the length Liam painted: \(72 \times \frac{3}{8} = 9 \times 3 = 27\) feet. Next, find the length of the remaining portion: \(72 - 27 = 45\) feet. Then, calculate the length Chloe painted, which is \(\frac{1}{3}\) of the remaining part: \(45 \times \frac{1}{3} = 15\) feet. Finally, find the difference between the lengths they painted: \(27 - 15 = 12\) feet. Liam painted 12 more feet than Chloe.

2

A rectangular painting is \(3\frac{1}{2}\) feet long and \(2\frac{1}{4}\) feet wide. An artist covers \(\frac{2}{3}\) of the painting with a protective glaze. What is the area of the glazed portion of the painting in square feet?

\(5\frac{1}{4}\) square feet

\(7\frac{7}{8}\) square feet

\(11\frac{13}{16}\) square feet

\(3\frac{5}{6}\) square feet

Explanation

First, calculate the total area of the painting by multiplying its length and width. Convert mixed numbers to improper fractions: \(3\frac{1}{2} = \frac{7}{2}\) and \(2\frac{1}{4} = \frac{9}{4}\). Area = \(\frac{7}{2} \times \frac{9}{4} = \frac{63}{8}\) square feet. Next, find \(\frac{2}{3}\) of this area: \(\frac{63}{8} \times \frac{2}{3} = \frac{126}{24}\). Simplify by dividing the numerator and denominator by their greatest common divisor, 6: \(\frac{21}{4}\). Convert this to a mixed number: \(5\frac{1}{4}\) square feet.

3

A water tank is currently filled with 45 gallons of water, which is \(\frac{3}{5}\) of its total capacity. What is the total capacity of the tank in gallons?

30 gallons

27 gallons

75 gallons

90 gallons

Explanation

Let C be the total capacity. The problem states that \(\frac{3}{5}\) of the total capacity is 45 gallons, so \(\frac{3}{5}C = 45\). To find C, divide 45 by \(\frac{3}{5}\): \(C = 45 \div \frac{3}{5} = 45 \times \frac{5}{3} = \frac{225}{3} = 75\). The total capacity is 75 gallons.

4

A bicycle originally priced at $320 is on sale for \(\frac{1}{4}\) off the original price. A customer also has a coupon for an additional \(\frac{1}{5}\) off the sale price. What is the final price the customer pays for the bicycle?

$176

$192

$224

$240

Explanation

First, calculate the sale price. A discount of \(\frac{1}{4}\) means the price is \(1 - \frac{1}{4} = \frac{3}{4}\) of the original. Sale price = \($320 \times \frac{3}{4} = $240\). The coupon gives an additional \(\frac{1}{5}\) off this sale price, so the customer pays \(1 - \frac{1}{5} = \frac{4}{5}\) of the sale price. Final price = \($240 \times \frac{4}{5} = $192\).

5

A hiking trail is \(12\frac{1}{2}\) kilometers long. A hiker has completed \(\frac{2}{5}\) of the trail. How many kilometers has the hiker traveled?

\(7\frac{1}{2}\) km

\(31\frac{1}{4}\) km

\(4\frac{4}{5}\) km

5 km

Explanation

To find the distance traveled, multiply the total length of the trail by the fraction completed. First, convert the mixed number to an improper fraction: \(12\frac{1}{2} = \frac{25}{2}\). Now multiply: \(\frac{25}{2} \times \frac{2}{5}\). You can simplify by canceling the 2s and dividing 25 by 5: \(\frac{25}{2} \times \frac{2}{5} = \frac{5}{1} \times \frac{1}{1} = 5\). The hiker has traveled 5 kilometers.

6

A baker has \(13\frac{1}{2}\) cups of sugar. A recipe for one batch of muffins requires \(\frac{3}{4}\) cup of sugar. How many full batches of muffins can the baker make?

10

17

18

20

Explanation

To find the number of batches, divide the total amount of sugar by the amount needed per batch. First, convert the mixed number to an improper fraction: \(13\frac{1}{2} = \frac{27}{2}\). Now, divide: \(\frac{27}{2} \div \frac{3}{4} = \frac{27}{2} \times \frac{4}{3}\). Simplify by cross-cancellation: \(27 \div 3 = 9\) and \(4 \div 2 = 2\). The calculation becomes \(\frac{9}{1} \times \frac{2}{1} = 18\). The baker can make exactly 18 full batches.

7

A running track is \(\frac{1}{4}\) of a mile long. A runner completed several laps, running a total of \(3\frac{1}{2}\) miles. How many laps did the runner complete?

12 laps

16 laps

14 laps

\(\frac{7}{8}\) laps

Explanation

This is a division problem involving mixed numbers and fractions. When you need to find how many times one quantity fits into another, you divide the total by the individual amount.

To find the number of laps, you need to divide the total distance by the length of one lap: $$3\frac{1}{2} \div \frac{1}{4}$$

First, convert the mixed number to an improper fraction: $$3\frac{1}{2} = \frac{7}{2}$$

Now divide: $$\frac{7}{2} \div \frac{1}{4}$$

Remember that dividing by a fraction is the same as multiplying by its reciprocal: $$\frac{7}{2} \times \frac{4}{1} = \frac{28}{2} = 14$$

The runner completed 14 laps, making D correct.

Looking at the wrong answers: A) $$\frac{7}{8}$$ laps results from incorrectly multiplying $$3\frac{1}{2} \times \frac{1}{4}$$ instead of dividing—this gives you a fraction of a lap, which doesn't make sense when someone ran multiple miles. B) 12 laps comes from converting $$3\frac{1}{2}$$ incorrectly to $$\frac{6}{2}$$ and then calculating $$\frac{6}{2} \times 4 = 12$$. C) 16 laps results from converting $$3\frac{1}{2}$$ to 4 (rounding up) and then multiplying by 4.

When solving "how many times" problems, always ask yourself whether your answer makes logical sense. If someone ran $$3\frac{1}{2}$$ miles on a $$\frac{1}{4}$$-mile track, they must have completed more than 3 laps but fewer than 20, which helps you verify that 14 is reasonable.

8

In a school band, \(\frac{3}{5}\) of the members play a brass instrument. Of those who play a brass instrument, \(\frac{1}{3}\) play the trumpet. If there are 12 trumpet players, how many members are in the band in total?

36

45

60

72

Explanation

First, determine the fraction of the entire band that plays the trumpet. This is \(\frac{3}{5} \times \frac{1}{3} = \frac{3}{15} = \frac{1}{5}\). So, \(\frac{1}{5}\) of the total band members are trumpet players. If T is the total number of members, then \(\frac{1}{5}T = 12\). To find T, multiply 12 by 5: \(12 \times 5 = 60\). There are 60 members in the band.

9

For a student's final grade, the average of three tests counts for \(\frac{2}{3}\) of the grade, and a final exam counts for the remaining \(\frac{1}{3}\). The student's test scores are 80, 90, and 100. If the student scores an 84 on the final exam, what is the student's final grade?

86

88

88.5

90

Explanation

First, find the average of the three test scores: \((80 + 90 + 100) \div 3 = 270 \div 3 = 90\). This average counts for \(\frac{2}{3}\) of the final grade, so its contribution is \(90 \times \frac{2}{3} = 60\) points. The final exam score is 84, and it counts for \(\frac{1}{3}\) of the grade, so its contribution is \(84 \times \frac{1}{3} = 28\) points. The final grade is the sum of these two parts: \(60 + 28 = 88\).

10

After a party, \(\frac{1}{4}\) of a pizza was left over. The next day, David ate \(\frac{2}{3}\) of the leftover pizza. The piece David ate weighed 6 ounces. What was the original weight of the whole pizza in ounces?

24 ounces

36 ounces

16 ounces

9 ounces

Explanation

This is a two-step problem working backwards. Let L be the weight of the leftover pizza. David ate \(\frac{2}{3}\) of L, which weighed 6 ounces. So, \(\frac{2}{3}L = 6\). To find L, calculate \(6 \div \frac{2}{3} = 6 \times \frac{3}{2} = 9\) ounces. So, the leftover pizza weighed 9 ounces. This leftover amount was \(\frac{1}{4}\) of the original pizza's weight, P. So, \(\frac{1}{4}P = 9\). To find P, calculate \(9 \div \frac{1}{4} = 9 \times 4 = 36\) ounces.

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