Question 43449
Speed of 1st car is 40 mph. This means in 1 hr. it travels 40 miles.
Speed of 2nd car is 55 mph. This means in 1 hr. it travels 55 miles.
So after 1 hr. the distance between them will be (55 - 40) = 15 miles.


In other way, the distance between the cars will be 15 miles after 1 hour.
So, the distance between the cars will be 1 mile after {{{1/15}}} hour.
So, the distance between the cars will be 5 miles after {{{(1/15)5 = 1/3}}} hour.


So the cars will be 5 miles apart after {{{1/3}}} hour i.e. 20 mins.