Back to Elementary Algebra 2e

8.7 Solve Proportion and Similar Figure Applications

Cross products for solving a proportion, and corresponding sides of similar triangles used to recover unknown heights, lengths, and map distances.

Elementary Algebra 2e, 8.7 Solve Proportion and Similar Figure Applications

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52 exercises

8.7 Exercise 1

If you miss a problem, go back to the section listed and review the material.

Solve n3=30\frac{n}{3} = 30.
If you missed this problem, review the reference.

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8.7 Exercise 2

The perimeter of a triangular window is 23 feet. The lengths of two sides are ten feet and six feet. How long is the third side?
If you missed this problem, review the reference.

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8.7 Exercise 4

Solve the proportion: n84=1112.\frac{n}{84} = \frac{11}{12} .

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8.7 Exercise 5

Solve the proportion: y96=1312.\frac{y}{96} = \frac{13}{12} .

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8.7 Exercise 7

Solve the proportion: 91b=75.\frac{91}{b} = \frac{7}{5} .

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8.7 Exercise 8

Solve the proportion: 39c=138.\frac{39}{c} = \frac{13}{8} .

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8.7 Exercise 10

Solve the proportion: yy+55=38.\frac{y}{y + 55} = \frac{3}{8} .

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8.7 Exercise 11

Solve the proportion: zz−84=−15.\frac{z}{z - 84} = - \frac{1}{5} .

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8.7 Exercise 13

Solve: v+308=v+6612.\frac{v + 30}{8} = \frac{v + 66}{12} .

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8.7 Exercise 14

Solve: 2x+159=7x+315.\frac{2 x + 15}{9} = \frac{7 x + 3}{15} .

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8.7 Exercise 16

Pediatricians prescribe 5 milliliters (ml) of acetaminophen for every 25 pounds of a child’s weight. How many milliliters of acetaminophen will the doctor prescribe for Emilia, who weighs 60 pounds?

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8.7 Exercise 17

For every 1 kilogram (kg) of a child’s weight, pediatricians prescribe 15 milligrams (mg) of a fever reducer. If Isabella weighs 12 kg, how many milligrams of the fever reducer will the pediatrician prescribe?

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8.7 Exercise 19

At a fast-food restaurant, a 22-ounce chocolate shake has 850 calories. How many calories are in their 12-ounce chocolate shake? Round your answer to nearest whole number.

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8.7 Exercise 20

Yaneli loves Starburst candies, but wants to keep her snacks to 100 calories. If the candies have 160 calories for 8 pieces, how many pieces can she have in her snack?

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8.7 Exercise 22

Yurianna is going to Europe and wants to change $800 dollars into Euros. At the current exchange rate, $1 US is equal to 0.738 Euro. How many Euros will she have for her trip?

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8.7 Exercise 23

Corey and Nicole are traveling to Japan and need to exchange $600 into Japanese yen. If each dollar is 94.1 yen, how many yen will they get?

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8.7 Exercise 26

ΔABC\Delta A B C is similar to ΔXYZ\Delta X Y Z. The lengths of two sides of each triangle are given in the figure.

Find the length of side yy.

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8.7 Exercise 29

Using the map above, find the distance from Portland to Boise.

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8.7 Exercise 31

A telephone pole casts a shadow that is 50 feet long. Nearby, an 8 foot tall traffic sign casts a shadow that is 10 feet long. How tall is the telephone pole?

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8.7 Exercise 32

A pine tree casts a shadow of 80 feet next to a 30-foot tall building which casts a 40 feet shadow. How tall is the pine tree?

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8.7 Exercise 33

Solve.

x56=78\frac{x}{56} = \frac{7}{8}

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8.7 Exercise 35

Solve.

4963=z9\frac{49}{63} = \frac{z}{9}

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8.7 Exercise 37

Solve.

5a=65117\frac{5}{a} = \frac{65}{117}

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8.7 Exercise 39

Solve.

98154=−7p\frac{98}{154} = \frac{−7}{p}

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8.7 Exercise 41

Solve.

a−8=−4248\frac{a}{−8} = \frac{−42}{48}

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8.7 Exercise 43

Solve.

2.7j=0.90.2\frac{2.7}{j} = \frac{0.9}{0.2}

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8.7 Exercise 45

Solve.

aa+12=47\frac{a}{a + 12} = \frac{4}{7}

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8.7 Exercise 47

Solve.

cc−104=−58\frac{c}{c - 104} = - \frac{5}{8}

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8.7 Exercise 49

Solve.

m+9025=m+3015\frac{m + 90}{25} = \frac{m + 30}{15}

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8.7 Exercise 51

Solve.

2p+48=p+186\frac{2 p + 4}{8} = \frac{p + 18}{6}

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8.7 Exercise 53

Solve.

Pediatricians prescribe 5 milliliters (ml) of acetaminophen for every 25 pounds of a child’s weight. How many milliliters of acetaminophen will the doctor prescribe for Jocelyn, who weighs 45 pounds?

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8.7 Exercise 55

Solve.

A veterinarian prescribed Sunny, a 65 pound dog, an antibacterial medicine in case an infection emerges after her teeth were cleaned. If the dosage is 5 mg for every pound, how much medicine was Sunny given?

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8.7 Exercise 57

Solve.

A new energy drink advertises 106 calories for 8 ounces. How many calories are in 12 ounces of the drink?

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8.7 Exercise 59

Solve.

A new 7 ounce lemon ice drink is advertised for having only 140 calories. How many ounces could Sally drink if she wanted to drink just 100 calories?

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8.7 Exercise 61

Solve.

Janice is traveling to Canada and will change $250 US dollars into Canadian dollars. At the current exchange rate, $1 US is equal to $1.01 Canadian. How many Canadian dollars will she get for her trip?

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8.7 Exercise 63

Solve.

Steve changed $600 into 480 Euros. How many Euros did he receive for each US dollar?

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8.7 Exercise 65

Solve.

When traveling to Great Britain, Bethany exchanged her $900 into 570 British pounds. How many pounds did she receive for each American dollar?

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8.7 Exercise 67

Solve.

Ronald needs a morning breakfast drink that will give him at least 390 calories. Orange juice has 130 calories in one cup. How many cups does he need to drink to reach his calorie goal?

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8.7 Exercise 69

Solve.

Elizabeth is returning to the United States from Canada. She changes the remaining 300 Canadian dollars she has to $230.05 in American dollars. What was $1 worth in Canadian dollars?

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8.7 Exercise 71

Solve.

A golden retriever weighing 85 pounds has diarrhea. His medicine is prescribed as 1 teaspoon per 5 pounds. How much medicine should he be given?

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8.7 Exercise 73

Solve.

Karen eats 12\frac{1}{2} cup of oatmeal that counts for 2 points on her weight loss program. Her husband, Joe, can have 3 points of oatmeal for breakfast. How much oatmeal can he have?

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8.7 Exercise 75

side b

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8.7 Exercise 77

Find the length of side d.

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8.7 Exercise 79

Find the actual distance from New York to Memphis.

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8.7 Exercise 81

Find the actual distance from New Orleans to Miami.

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8.7 Exercise 83

A 2 foot tall dog casts a 3 foot shadow at the same time a cat casts a one foot shadow. How tall is the cat?

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8.7 Exercise 85

The tower portion of a windmill is 212 feet tall. A six foot tall person standing next to the tower casts a seven foot shadow. How long is the windmill’s shadow?

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8.7 Exercise 87

Heart Rate At the gym, Carol takes her pulse for 10 seconds and counts 19 beats.

  1. ⓐ How many beats per minute is this?
  2. ⓑ Has Carol met her target heart rate of 140 beats per minute?
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8.7 Exercise 89

Cost of a Road Trip Jesse’s car gets 30 miles per gallon of gas.

  1. ⓐ If Las Vegas is 285 miles away, how many gallons of gas are needed to get there and then home?
  2. ⓑ If gas is $3.09 per gallon, what is the total cost of the gas for the trip?
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8.7 Exercise 91

Lawn Fertilizer Phil wants to fertilize his lawn. Each bag of fertilizer covers about 4,000 square feet of lawn. Phil’s lawn is approximately 13,500 square feet. How many bags of fertilizer will he have to buy?

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8.7 Exercise 93

Cooking Natalia’s pasta recipe calls for 2 pounds of pasta for 1 quart of sauce. How many pounds of pasta should Natalia cook if she has 2.5 quarts of sauce?

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8.7 Exercise 95

Marisol solves the proportion 144a=94\frac{144}{a} = \frac{9}{4} by ‘cross multiplying’, so her first step looks like 4·144=9·a.4 \cdot 144 = 9 \cdot a . Explain how this differs from the method of solution shown in the example.

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Adapted from Elementary Algebra 2e © 2020 Rice University. Licensed under CC BY 4.0. Source: Elementary Algebra 2e. Imported at revision 77a933c.