A salesman travels a distance of 70 miles in 5 hours. How much faster, in miles per hour, must he travel to make the same trip in 75 hours less than the original time?

A 28

B 24

C 12

D None of these

Correct Answer: Option C

The salesman has to make it in (2.5 - 0.75)hrs = 1.75 hours

Now, Original speed, s = 70/2.5 = 28 miles/hr

Now,

with the changed time,

changed speed, S' = distance/ changed time

S' = 70/1.75 = 40 mile/hr

Now,

change from the original speed = 40 - 28 = 12 mile/hr