Question

2. A man drove 240 miles south at the rate of 60 miles per hour. On the return trip, he drove the rate of 40 miles per hour. The average rate per hour for the round trip was:​

Answer 1

48 mph

Explanation:

Distance = rate x time

Going: Rate is 60 mph distance is 240

The time is the
`(Distance)/(rate)` or
`(240)/(60)` or 4 hours.

Coming: Rate is 40 mph distance is 240

The time is the
`(distance)/(rate)` or
`(240)/(40)` or 6 hours.

We can now find the average.

Average rate =
`(total distance)/(total time)` =
`(480)/(10)` = 48 mph

Answer 2

`av = (v_(2) - v_(1))/(t_(2) - t_(1))`

`t_(1) = (d)/(v_(1)) = (240)/(60) = 4 \: hours \\ t_(2) = (d)/(v_(2)) = (240)/(40) = 6 \: hours`

`av = (v_(2) - v_(1))/(t_(2) - t_(1)) = (40 - 60)/(6 - 4) = ( - 20)/(2) = - 10`

`av \: speed= 10 \\ av \: velocity = - 10 \: \: north`