Basic Mathematics for College Students

98. BUILDING A PIER Apile driveruses a heavy
    weight to pound tall poles into the ocean floor. If
    each strike of a pile driver on the top of a pole sends
    it 6 inches deeper, find the depth of the pole after
    20 strikes.


99. MAGNIFICATION A mechanic used an electronic
    testing device to check the smog emissions of a car.
    The results of the test are displayed on a screen.
    a. Find the high and low values for this test as
    shown on the screen.
    b. By switching a setting, the picture on the screen
    can be magnified. What would be the new high
    and new low if every value were doubled?


100. LIGHT Sunlight is a mixture of all colors. When
     sunlight passes through water, the water absorbs
     different colors at different rates, as shown.
     a. Use a signed number to represent the depth to
     which red light penetrates water.
     b. Green light penetrates 4 times deeper than red
     light. How deep is this?
     c. Blue light penetrates 3 times deeper than orange
     light. How deep is this?

Depth of water (ft)

–10

–20

–30

–40

R

E

D

S

O R A N G E S

Y E L L O W S

Surface of water

− 5

5

Smog

emission

testing

Normal

Magnify

 2

High

Low

174 Chapter 2 The Integers

Image Source/Getty Images

101. JOB LOSSES Refer to the bar graph. Find the
     number of jobs lost in...
     a. September 2008 if it was about 6 times the
     number lost in April.
     b. October 2008 if it was about 9 times the number
     lost in May.
     c. November 2008 if it was about 7 times the
     number lost in February.
     d. December if it was about 6 times the number lost
     in March.

Source: Bureau of Labor Statistics

102. RUSSIA The U.S. Census Bureau estimates that
     Russia’s population is decreasing by about 700,000
     per year because of high death rates and low birth
     rates. If this pattern continues, what will be the
     total decline in Russia’s population over the next
     30 years? (Source: About.com)


103. PLANETS The average surface temperature of Mars
     is. Find the average surface temperature of
     Uranus if it is four times colder than Mars. (Source:
     The World Almanac and Book of Facts,2009)


104. CROP LOSS A farmer, worried about his fruit
     trees suffering frost damage, calls the weather
     service for temperature information. He is told that
     temperatures will be decreasing approximately
     5 degrees every hour for the next five hours. What
     signed number represents the total change in
     temperature expected over the next five hours?


105. TAX WRITE-OFF For each of the last six years,
     a businesswoman has filed a $200 depreciation
     allowance on her income tax return for an office
     computer system. What signed number represents
     the total amount of depreciation written off over
     the six-year period?


106. EROSION A levee protects a town in a low-lying
     area from flooding. According to geologists, the
     banks of the levee are eroding at a rate of 2 feet
     per year. If something isn’t done to correct the
     problem, what signed number indicates how
     much of the levee will erode during the next
     decade?

81°F

–76

–150

–100

–120

–75

Net jobs lost (in thousands)

2008 U.S. Monthly Net Job Losses

Jan.

–83

Feb.

–88

Mar.

–67

Apr.

–47

May June

–100

July

–67

–127

Aug.

–50

–25