SOLUTION: Juan rides his bike from Lawrence to Salisbury beach (30 miles in 3 hours). He divides distance (miles) by time (hours) and sees that his overall average speed is 10mph. He buys
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Question 270018: Juan rides his bike from Lawrence to Salisbury beach (30 miles in 3 hours). He divides distance (miles) by time (hours) and sees that his overall average speed is 10mph. He buys 3 Power bars and eats them. How fast (mph) must he return so that his overall average speed for the round trip (60 miles) is 15mph?
THE ANSWER IS NOT 20mph. Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website! You don't take an average of 2 averages to get
an overall average. The correct way to do it is:
(total distance travelled)/(total time for trips) = average speed
Let = his time in hrs for return trip mi/hr
Multiply both sides by hr
It will take him 1 hr to make the 30 mi return trip, so
return speed = mi/hr
check answer:
OK
