Question

Bank robber holds up a bank and speeds off at 71 mph. Police start chasing him 10 minutes later going 78 mph. How long will it take to catch up to them?

Answer 1

It takes 1.68 hours to catch up to them.

Explanation:

The speed of robber = 71 mph

The speed of police = 78 mph

The police start 10 minutes later

by that time robber would have travelled

`distance = (speed)/(time)`

10 minutes =0.166667 hours

then the distance = 11.8 mph

Let them meet at distance x from the bank.

time taken by police to reach x , time =
`( x)/(78)`----------------------(1)

time taken by robber in the same time =
`(x-11.8)/(71)`---------------(2)

Equating (1) and (2)

`(x)/(78) =( x-11.8)/(71)`

`71 x = 78(x - 11.8)`

71x =78x - 920.4

920.4 = 78x - 71x

920.4 = 7x

x = 131.48

The distance where they catch up with the robber from the bank is 131.48 miles

speed of police = 78 mph

distance = 131.48 miles

time they catch up =
`(131.48)/(78)`

= 1.68 hours