Question

A motorist made a 60-mile trip averaging 20 miles per hour.On the return trip,he averaged 30 miles per hour.What was the motorist's average speed for the entire trip?

Answer 1

The average speed of entire journey is 24 miles per hour.

Explanation:

It is given that, the speed while going away trip was 20 miles per hour and return journey was 30 miles per hour.

The total distance is 60 miles.

The time taken for first journey is ,

t1 =
`(Distance)/(average speed)` =
`(60)/(20)` = 3 hours

Similarly, the time taken for second journey is,

t2 =
`(60)/(30)` = 2 hours

Thus the total time taken is, t1+t2 = T

T = 3 + 2 = 5 hours.

The total distance travelled in full journey is 120 miles( 2 X 60)

Thus the average speed for entire trip is,

speed =
`(Distance)/(total time)` =
`(120)/(5)`

= 24 miles per hour