SOLUTION: Joanne left the driveway 40 seconds after Gloria driving down a winding four mile country road. If Joanne's speed averaged 25 miles an hour what would Gloria's average speed be fo

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Question 233179: Joanne left the driveway 40 seconds after Gloria driving down a winding four mile country road. If Joanne's speed averaged 25 miles an hour what would Gloria's average speed be for Joanne to catch up to her after the third mile?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Joanne left the driveway 40 seconds after Gloria driving down a winding four mile country road.
If Joanne's speed averaged 25 miles an hour what would Gloria's average speed be for Joanne to catch up to her after the third mile?
:
Let s = Gloria's speed to catch Joanne
;
Let this happen at 3.1 miles
:
Change 40 sec to hrs
40%2F3600 = .011 hrs
:
Write a time equation (Time = dist%2Fspeed)
;
J.s travel time = G's travel time + 40 sec (.011 hrs)
3.1%2F25 = 3.1%2Fs + .011
:
multiply equation by 25s
3.1s = 3.1*25 + .011(25s)
:
3.1s = 77.5 + .275s
3.1s - .275s = 77.5
2.825s = 77.5
s = 77.5%2F2.825
s = 27.43 mph
:
:
Check by finding the times
3.1/25 = .124 hrs
3.1/27.43 = .113 hrs
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time diff = .011 hrs which is: .011 * 3600 ~ 40 sec