Question

An automobile traveled 7 hours at an average

speed of 50 miles per hour. It averaged only 40
miles per hour on the return trip. The average
speed per hour, to the NEAREST mile, for the
round trip was
(A)46 miles per hour
(B) 44 miles per hour
(C)43 miles per hour
(D) 47 miles per hour

Answer 1

(B) 44 miles per hour

Explanation:

We are given that

Speed, v1=50 miles/hr

Time, t1=7 hours

Average speed, v2=40 miles/hr

We have to find the average speed per hour for the round trip .

Distance traveled by automobile from one side

d1=
`v_1t=50* 7=350`miles

d1=d2=350 miles

Total distance=d1+d2=350+350=700 miles

Now,

`t2=(d_2)/(v_2)=(350)/(40)=8.75 hour`

Total time=t1+t2=7+8.75=15.75 hours

Now, average speed for the round tripe

=
`(total\;distance)/(total\;time)`

=
`(700)/(15.75)=44.4\approx 44`miles/hr

Hence, option (B) is correct.