SOLUTION: A test driver has to drive a car on a 1-mile track for two rounds in a way that his average speed is 60 mph on his first round his average speed is 40 mph how fast does he need to

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Question 1043235: A test driver has to drive a car on a 1-mile track for two rounds in a way that his average speed is 60 mph on his first round his average speed is 40 mph how fast does he need to drive to get the right speed average?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You have to start with the definition of average speed
It is: [ total distance ] / [ total time ]
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The total distance is twice around the track = +2+ mi
So far, using the definition, I have:
+60+=+2+%2F+t+
where +t+ = total time
+60t+=+2+
+t+=+1%2F30+ hr
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For the 1st mile:
+1+=+40%2At%5B1%5D+
+t%5B1%5D+=+1%2F40+ hr
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His time for the 2nd mile is:
+1%2F30+-+1%2F40+=+4%2F120+-+3%2F120+
+1%2F30+-+1%2F40+=+1%2F120+
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Let +s+ = his speed for the 2nd mile
+1+=+s%2A%281%2F120+%29+
+s+=+120+
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He needs a speed of 120 mi/hr for the 2nd mile
in order to average 60 mi/hr for the 2 miles.
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check my math also