Question 910599: Mark works out for 50 minutes by biking and jogging. He bikes at an average rate of 1200 feet per minute for x minutes. He jogs at an average rate of 900 feet per minute. He wants to travel a combined 10 miles. How many minutes did Mark spend biking?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Mark works out for 50 minutes by biking and jogging.
He bikes at an average rate of 1200 feet per minute for x minutes.
He jogs at an average rate of 900 feet per minute.
He wants to travel a combined 10 miles.
How many minutes did Mark spend biking?
:
Let j = time jogging (in minutes)
let b = time biking
then
j + b = 50
j = (50-b), use this form for substitution
:
Change 10 mi to ft: 10 * 5280 = 52,800 ft
:
1200b + 900j = 52800
Simplify, divide by 100
12b + 9j = 528
substitute (50-b) for j
12b + 9(50-b) = 528
12b + 450 - 9b = 528
12b - 9b = 528 - 450
3b = 78
b = 78/3
b = 26 min biking
:
:
Check this, we know that he spent 50 - 26 = 24 min jogging
26*1200 = 31200 ft biking
24*900 = 21600 ft jogging
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total dist: 52800 which is 10 mi
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