Question

What do you want to find out? > The rate at which Bill puts shringles on a rood. What do you know? > Bill and Chip each finished half of the roof. > Bill needs 7 hours to put the same number of shingles on the roof that Chip does in 4 hours. > For each worker, the time multiplied by the rate equals the number of shringles > Chip's rate is 30 shringles more per hour than Bill's rate. What is Chip's rate in terms of Bill's rate? Let b = Bill's rate. Chip's rate = Bill's rate (b) ( - ) ( 4 ) ( 30 ) ( 7 ) ( + )

Answer 1

(a) b = (4/7)c

(b) Bill: 40 shingles/hour; Chip: 70 shingles/hour

Explanation:

Let b and c represent Bill's and Chip's rates in shingles per hour, respectively. Then we have ...

7b = 4c

c - b = 30 . . . . shingles per hour difference in rates

(a) Bill's rate in terms of Chip's rate can be found by dividing the first equation by 7

b = (4/7)c . . . . . Bill's rate is 4/7 of Chip's rate

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(b) To find the rates, we can multiply the second equation by 7 and substitute using the first equation:

7c -7b = 210

7c -4c = 210

c = 210/3 = 70

b = (4/7)(70) = 40

Bill's rate is 40 shingles per hour; Chip's rate is 70 shingles per hour.