Intermediate Algebra (11th edition)

Concept Check Answer each question.

25.A boat goes 20 mph in still water, and the rate of the current is tmph.

(a)What is the rate of the boat when it travels upstream?

(b) What is the rate of the boat when it travels downstream?

26. (a)If it takes mhours to grade a set of papers, what is the grader’s rate (in job per hour)?
    (b) How much of the job will the grader do in 2 hr?

Solve each problem. See Examples 2 and 3.

520 CHAPTER 9 Quadratic Equations, Inequalities, and Functions

drt

Upstream 4

Downstream 16

x- 15

drt

With Wind 810

Against Wind 720

Fractional

Time Working Part of the

Rate Together Job Done

2

2

1

x

Faster

Worker

Slower

Worker

Fractional

Time Working Part of the

Rate Together Job Done

Faster

Worker

Slower

Worker

Lodi

Jackson

Manteca

CALIFORNIA

40 mi

40 mi Medicine Hat

Cranbrook

BRITISH

COLUMBIA

ALBERTA

300 km

27.On a windy day William Kunz found

that he could go 16 mi downstream and

then 4 mi back upstream at top speed in

a total of 48 min. What was the top

speed of William’s boat if the rate of the

current was 15 mph?

28.Vera Koutsoyannis flew her plane for

6 hr at a constant rate. She traveled

810 mi with the wind, then turned

around and traveled 720 mi against the

wind. The wind speed was a constant

15 mph. Find the rate of the plane.

29.The distance from Jackson to Lodi is

about 40 mi, as is the distance from

Lodi to Manteca. Adrian Iorgoni drove

from Jackson to Lodi, stopped in Lodi

for a high-energy drink, and then drove

on to Manteca at 10 mph faster. Driving

time for the entire trip was 88 min. Find

the rate from Jackson to Lodi. (Source:

State Farm Road Atlas.)

30.Medicine Hat and Cranbrook are 300 km

apart. Steve Roig-Watnik rides his Harley

20 km per hr faster than Mohammad

Shakil rides his Yamaha. Find Steve’s

average rate if he travels from Cran-

brook to Medicine Hat in hr less time

than Mohammad. (Source: State Farm

Road Atlas.)

(^114)
31.Working together, two people can cut a
large lawn in 2 hr. One person can do the
job alone in 1 hr less time than the other.
How long (to the nearest tenth) would it
take the faster worker to do the job?
(Hint: xis the time of the faster worker.)
32.Working together, two people can clean
an office building in 5 hr. One person is
new to the job and would take 2 hr
longer than the other person to clean the
building alone. How long (to the nearest
tenth) would it take the new worker to
clean the building alone?