Emilio left Sunshine Road at 8:30 A.M. and arrived at Summer Lane at 1:30 P.M. His average speed for the whole journey was 60 km per hour. For the first 60% of the trip, he drove at an average speed at of 90 km per hour. For the next 25% of the remaining trip, his average speed was 60 km per hour. Find his average speed for the remaining part of the trip.

3 answers

The average speed for the whole trip was 60 km/h
the total time is 5 hours, so the total distance = 300 km
time for first leg = .6(300)/90 = 2 hours
time for 2nd leg = .25(.4)(300)/60 = .5 hours
leaving him with 2.5 hours for the last part
distance he still has to go = 300 - .6(300) - .25(.4)(300) = 90 km

so speed for last leg = 90/2.5 = 36 km/h

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