What was the average speed for the entire trip?

Question

The jones family took a 600 mile trip to the mountains last spring and averaged 50 miles per hour on the trip. On the return tripthey averaged 55 miles per hour.

Answer 1

distance=rate*time

600=50*t

t=600/50

t=12 hours to the mountains

 

600=55*t

t=600/55

t=10.91 hours returning from the mountains

total distance=rate*total time

total distance=600+600=1200 miles

total time=12+10.91=22.91 hours

1200=rate*22.91

rate=1200/22.91

rate=52.3788 miles per hour is the average speed for the entire trip

 

another solution is to use the harmonic mean; you can look it up if you don't know it

in its simplest form you have....

(2*rate1*rate2)/(rate1+rate2)

(2*50*55)/(50+55)

5500/105

simplify or divide the way it is

5500/105=52.38 mph