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Chapter 8 Review Exercises

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Chapter Review Exercises

Simplify Rational Expressions

Determine the Values for Which a Rational Expression is Undefined

In the following exercises, determine the values for which the rational expression is undefined.

Exercise 1

2a+13a2

Answer

a23

Exercise 2

b3b216

Exercise 3

3xy25y

Answer

y0

Exercise 4

u3u2u30

Evaluate Rational Expressions

In the following exercises, evaluate the rational expressions for the given values.

Exercise 5

4p1p2+5 when p=1

Answer

56

Exercise 6

q25q+3 when q=7

Exercise 7

y28y2y2 when y=1

Answer

72

Example 8

z2+24zz2 when z=3

Simplify Rational Expressions

In the following exercises, simplify.

Exercise 9

1024

Answer

512

Exercise 10

8m416mn3

Exercise 11

14a14a1

Answer

14

Exercise 12

b2+7b+12b2+8b+16

Simplify Rational Expressions with Opposite Factors

In the following exercises, simplify.

Exercise 13

c2c24c2

Answer

c+1c+2

Exercise 14

d1616d

Exercise 15

7v3525v2

Answer

75+v

Exercise 16

w23w2849w2

Multiply and Divide Rational Expressions

Multiply Rational Expressions

In the following exercises, multiply.

Exercise 17

38·215

Answer

120

Exercise 18

2xy28y3·16y24x

Exercise 19

3a2+21aa2+6a7·a1ab

Answer

3b

Exercise 20

5z25z2+40z+35·z213z

Divide Rational Expressions

In the following exercises, divide.

Exercise 21

t24t12t2+8t+12÷t2366t

Answer

6t(t+6)2

Exercise 22

r2164÷r3642r28r+32

Exercise 23

11+ww9÷121w29w

Answer

111+w

Exercise 24

3y212y634y+3÷(6y242y)

Exercise 25

c2643c2+26c+16c24c3215c+10

Answer

5c+4

Exercise 26

8m28mm4·m2+2m24m2+7m+10÷2m26mm+5

​​​​​Add and Subtract Rational Expressions with a Common Denominator

Add Rational Expressions with a Common Denominator

In the following exercises, add.

Exercise 27

35+25

Answer

1

Exercise 28

4a22a112a1

Exercise 29

p2+10pp+5+25p+5

Answer

p+5

Exercise 30

3xx1+2x1

Subtract Rational Expressions with a Common Denominator

In the following exercises, subtract.

Exercise 31

d2d+43d+28d+4

Answer

d7

Exercise 32

z2z+10100z+10

Exercise 33

4q2q+3q2+6q+53q2+q+6q2+6q+5

Answer

q3q+5

Exercise 34

5t+4t+3t2254t28t32t225

Add and Subtract Rational Expressions whose Denominators are Opposites

In the following exercises, add and subtract.

Exercise 35

18w6w1+3w216w

Answer

15w+26w1

Exercise 36

a2+3aa243a84a2

Exercise 37

2b2+3b15b249b2+16b149b2

Answer

3b2b+7

Exercise 38

8y210y+72y5+2y2+7y+252y

Add and Subtract Rational Expressions With Unlike Denominators

Find the Least Common Denominator of Rational Expressions

In the following exercises, find the LCD.

Exercise 38

4m23m10,2mm2m20

Answer

(m+2)(m5)(m+4)

Exercise 39

6n24,2nn24n+4

Exercise 40

53p2+17p6,2m3p223p8

Answer

(3p+1)(p+6)(p+8)

Find Equivalent Rational Expressions

In the following exercises, rewrite as equivalent rational expressions with the given denominator.

Exercise 41

Rewrite as equivalent rational expressions with denominator (m+2)(m5)(m+4)

4m23m10,2mm2m20.

Exercise 42

Rewrite as equivalent rational expressions with denominator (n2)(n2)(n+2)

6n24n+4,2nn24.

Answer

6n+12(n2)(n2)(n+2),2n24n(n2)(n2)(n+2)

Exercise 43

Rewrite as equivalent rational expressions with denominator (3p+1)(p+6)(p+8)

53p2+19p+6,7p3p2+25p+8

​​​​​​Add Rational Expressions with Different Denominators

In the following exercises, add.

Exercise 44

23+35

Answer

1915

Exercise 45

75a+32b

Exercise 46

2c2+9c+3

Answer

11c12(c2)(c+3)

Exercise 47

3dd29+5d2+6d+9

Exercise 48

2xx2+10x+24+3xx2+8x+16

Answer

5x2+26x(x+4)(x+4)(x+6)

Exercise 49

5qp2qp2+4qq21

Subtract Rational Expressions with Different Denominators

In the following exercises, subtract and add.

Exercise 50

3vv+2v+2v+8

Answer

2(v2+10v2)(v+2)(v+8)

Exercise 51

3w15w2+w20w+24w

Exercise 52

7m+3m+25

Answer

2m7m+2

Exercise 53

nn+3+2n3n9n29

Exercise 54

8dd2644d+8

Answer

4d8

Exercise 55

512x2y+720xy3

Simplify Complex Rational Expressions

Simplify a Complex Rational Expression by Writing it as Division

In the following exercises, simplify.

Exercise 56

5aa+210a2a24

Answer

a22a

Exercise 57

25+5613+14

Exercise 58

x3xx+51x+5+1x5

Answer

(x8)(x5)2

Exercise 59

2m+mnnm1n

​​​​​​​Simplify a Complex Rational Expression by Using the LCD

In the following exercises, simplify.

Exercise 60

6+2q45q+4

Answer

(q2)(q+4)5(q4)

Exercise 61

3a21b1a+1b2

Exercise 62

2z249+1z+79z+7+12z7

Answer

z521z+21

Exercise 63

3y24y322y8+1y+4

Solve Rational Equations

Solve Rational Equations

In the following exercises, solve.

Exercise 64

12+23=1x

Answer

67

Exercise 65

12m=8m2

Exercise 66

1b2+1b+2=3b24

Answer

32

Exercise 67

3q+82q2=1

Exercise 68

v15v29v+18=4v3+2v6

Answer

no solution

Exercise 69

z12+z+33z=1z

Solve a Rational Equation for a Specific Variable

In the following exercises, solve for the indicated variable.

Exercise 70

Vl=hw for l

Answer

l=Vhw

Exercise 71

1x2y=5 for y

Exercise 72

x=y+5z7 for z

Answer

z=y+5+7xx

Exercise 73

P=kV for V

​​​​​​Solve Proportion and Similar Figure Applications Similarity

Solve Proportions

In the following exercises, solve.

Exercise 74

x4=35

Answer

125

Exercise 75

3y=95

Exercise 76

ss+20=37

Answer

15

Exercise 77

t35=t+29

​​​​​​​In the following exercises, solve using proportions.

Exercise 78

Rachael had a 21 ounce strawberry shake that has 739 calories. How many calories are there in a 32 ounce shake?

Answer

1161 calories

Exercise 79

Leo went to Mexico over Christmas break and changed $525 dollars into Mexican pesos. At that time, the exchange rate had $1 US is equal to 16.25 Mexican pesos. How many Mexican pesos did he get for his trip?

​​​​​​​Solve Similar Figure Applications

In the following exercises, solve.

Exercise 80

ABC is similar to XYZ. The lengths of two sides of each triangle are given in the figure. Find the lengths of the third sides.

This image shows two triangles. The large triangle is labeled A B C. The length from A to B is labeled 8. The length from B to C is labeled 7. The length from C to A is labeled b. The smaller triangle is triangle x y z. The length from x to y is labeled 2 and two-thirds. The length from y to z is labeled x. The length from x to z is labeled 3.

Answer

b=9; x=213

Exercise 81

On a map of Europe, Paris, Rome, and Vienna form a triangle whose sides are shown in the figure below. If the actual distance from Rome to Vienna is 700 miles, find the distance from

  1. a. Paris to Rome
  2. b. Paris to Vienna

This is an image of a triangle. Clockwise beginning at the top, each vertex is labeled. The top vertex is labeled “Paris”, the next vertex is labeled “Vienna”, and the next vertex is labeled “Rome”. The distance from Paris to Vienna is 7.7 centimeters. The distance from Vienna to Rome is 7 centimeters. The distance from Rome to Paris is 8.9 centimeters.

Exercise 82

Tony is 5.75 feet tall. Late one afternoon, his shadow was 8 feet long. At the same time, the shadow of a nearby tree was 32 feet long. Find the height of the tree.

Answer

23 feet

Exercise 83

The height of a lighthouse in Pensacola, Florida is 150 feet. Standing next to the statue, 5.5 foot tall Natalie cast a 1.1 foot shadow How long would the shadow of the lighthouse be?

​​​​​​​Solve Uniform Motion and Work Applications Problems

Solve Uniform Motion Applications

In the following exercises, solve.

Exercise 84

When making the 5-hour drive home from visiting her parents, Lisa ran into bad weather. She was able to drive 176 miles while the weather was good, but then driving 10 mph slower, went 81 miles in the bad weather. How fast did she drive when the weather was bad?

Answer

45 mph

Exercise 85

Mark is riding on a plane that can fly 490 miles with a tailwind of 20 mph in the same time that it can fly 350 miles against a tailwind of 20 mph. What is the speed of the plane?​​​​​​​

Exercise 86

John can ride his bicycle 8 mph faster than Luke can ride his bike. It takes Luke 3 hours longer than John to ride 48 miles. How fast can John ride his bike?

Answer

16 mph

Exercise 87

Mark was training for a triathlon. He ran 8 kilometers and biked 32 kilometers in a total of 3 hours. His running speed was 8 kilometers per hour less than his biking speed. What was his running speed?

​​​​​​​Solve Work Applications

In the following exercises, solve.

Exercise 88

Jerry can frame a room in 1 hour, while Jake takes 4 hours. How long could they frame a room working together?

Answer

45 hour

Exercise 89

Lisa takes 3 hours to mow the lawn while her cousin, Barb, takes 2 hours. How long will it take them working together?

Exercise 90

Jeffrey can paint a house in 6 days, but if he gets a helper he can do it in 4 days. How long would it take the helper to paint the house alone?

Answer

12 days

Exercise 91

Sue and Deb work together writing a book that takes them 90 days. If Sue worked alone it would take her 120 days. How long would it take Deb to write the book alone?

​​​​​​​Use Direct and Inverse Variation

Solve Direct Variation Problems

In the following exercises, solve.

Exercise 92

If y varies directly as x, when y=9 and x=3, find x when y=21.

Answer

7

Exercise 93

If y varies directly as x, when y=20 and x=2, find y when x=4.

Exercise 94

If m varies inversely with the square of n, when m=4 and n=6, find m when n=2.

Answer

36

Exercise 95

Vanessa is traveling to see her fiancé. The distance, d, varies directly with the speed, v, she drives. If she travels 258 miles driving 60 mph, how far would she travel going 70 mph?

Exercise 96

If the cost of a pizza varies directly with its diameter, and if an 8” diameter pizza costs $12, how much would a 6” diameter pizza cost?

Answer

$9

Exercise 97

The distance to stop a car varies directly with the square of its speed. It takes 200 feet to stop a car going 50 mph. How many feet would it take to stop a car going 60 mph?

​​​​​​​Solve Inverse Variation Problems

In the following exercises, solve.

Exercise 98

The number of tickets for a music fundraiser varies inversely with the price of the tickets. If Madelyn has just enough money to purchase 12 tickets for $6, how many tickets can Madelyn afford to buy if the price increased to $8?

Answer

97 tickets​​​​​​​

Exercise 99

On a string instrument, the length of a string varies inversely with the frequency of its vibrations. If an 11-inch string on a violin has a frequency of 360 cycles per second, what frequency does a 12-inch string have?​​​​​​​

Practice Test

In the following exercises, simplify.

Exercise 1

3a2b6ab2

Answer

a2b​​​​​​​

Exercise 2

5b25b225

​​​​​​​In the following exercises, perform the indicated operation and simplify.

Exercise 3

4xx+2·x2+5x+612x2

Answer

x+33x

Exercise 4

5y4y8·y2410

Exercise 5

4pq+5p

Answer

4+5qpq

Exercise 6

1z93z+9

Exercise 7

23+3525

Answer

1916

Exercise 8

1m1n1n+1m

In the following exercises, solve each equation.

Exercise 9

12+27=1x

Answer

x=1411

Exercise 10

5y6=3y+6

Exercise 11

1z5+1z+5=1z225

Answer

z=12

Exercise 12

t4=35

Exercise 13

2r2=3r1

Answer

r=4

In the following exercises, solve.

Exercise 14

If y varies directly with x, and x=5 when y=30, find x when y=42.

Exercise 15

If y varies inversely with x and x=6 when y=20, find y when x=2.

Answer

y=60

Exercise 16

If y varies inversely with the square of x and x=3 when y=9, find y when x=4.

Exercise 17

The recommended erythromycin dosage for dogs, is 5 mg for every pound the dog weighs. If Daisy weighs 25 pounds, how many milligrams of erythromycin should her veterinarian prescribe?

Answer

125 mg

Exercise 18

Julia spent 4 hours Sunday afternoon exercising at the gym. She ran on the treadmill for 10 miles and then biked for 20 miles. Her biking speed was 5 mph faster than her running speed on the treadmill. What was her running speed?

Exercise 19

Kurt can ride his bike for 30 miles with the wind in the same amount of time that he can go 21 miles against the wind. If the wind’s speed is 6 mph, what is Kurt’s speed on his bike?

Answer

14 mph

Exercise 20

Amanda jogs to the park 8 miles using one route and then returns via a 14-mile route. The return trip takes her 1 hour longer than her jog to the park. Find her jogging rate.

Exercise 21

An experienced window washer can wash all the windows in Mike’s house in 2 hours, while a new trainee can wash all the windows in 7 hours. How long would it take them working together?

Answer

159 hour

Exercise 22

Josh can split a truckload of logs in 8 hours, but working with his dad they can get it done in 3 hours. How long would it take Josh’s dad working alone to split the logs?

Exercise 23

The price that Tyler pays for gas varies directly with the number of gallons he buys. If 24 gallons cost him $59.76, what would 30 gallons cost?

Answer

$74.70

Exercise 24

The volume of a gas in a container varies inversely with the pressure on the gas. If a container of nitrogen has a volume of 29.5 liters with 2000 psi, what is the volume if the tank has a 14.7 psi rating? Round to the nearest whole number.

Exercise 25

The cities of Dayton, Columbus, and Cincinnati form a triangle in southern Ohio, as shown on the figure below, that gives the map distances between these cities in inches.

This is an image of a triangle. Clockwise beginning at the top, each vertex is labeled. The top vertex is labeled “Dayton”, the next vertex is labeled “Columbus”, and the next vertex is labeled “Cincinnati”. The distance from Dayton to Columbus is 3.2 inches. The distance from Columbus to Cincinnati is 5.3 inches. The distance from Cincinnati to Dayton is 2.4 inches.

The actual distance from Dayton to Cincinnati is 48 miles. What is the actual distance between Dayton and Columbus?

Answer

64 miles

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This page titled Chapter 8 Review Exercises is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by OpenStax via source content that was edited to the style and standards of the LibreTexts platform.

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