SOLUTION: in order to qualify for finals in racing event,a race car must achieve an average speed of 250km/hr on a track with a total length of 1600m.if a particular car covers the first hal

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Question 490838: in order to qualify for finals in racing event,a race car must achieve an average speed of 250km/hr on a track with a total length of 1600m.if a particular car covers the first half of the track at an average speed of 230km/hr,what minimum average speed must it have in the second half of the track in order to qualify
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
in order to qualify for finals in racing event, a race car must achieve an average speed of 250km/hr on a track with a total length of 1600m.
if a particular car covers the first half of the track at an average speed of 230km/hr, what minimum average speed must it have in the second half of the track in order to qualify
:
Let s = min average speed for the 2nd half of the track
Change the distances to .8 km and 1.6 km
Write a time equation, Time = dist/speed
:
.8%2F230 + .8%2Fs = 1.6%2F250
multiply by 57500s (230*250) to clear the denominators, results:
250s(.8) + 57500(.8) = 230s(1.6)
200s + 46000 = 368s
46000 = 368s - 200s
46000 = 168s
s = 46000%2F168
s = 273.8 km/hr to average 250 km.hr
:
:
You can confirm this by finding the actual times
.8%2F230 + .8%2F273.8 = 1.6%2F250