Question

Adam left the hospital and drove toward his cabin on the lake. Maria left one hour later driving 11 km/h faster in an effort to catch up to him. After four hours Maria finally caught up. Find Adam's average speed.

Answer 1

Answer: Adam's average speed is 33 mph.

Explanation:

Let x represent Adam's average speed.

By the time Maria catches up with Adam, they would have covered the same distance.

Distance = speed × time

Distance travelled by Adam after 4 hours is

4 × x = 4x

Maria left one hour later driving 11 km/h faster in an effort to catch up to him. This means that Maria's speed is (11 + x) mph and the time she spent travelling is 4 - 1 = 3 hours. Distance covered by Maria is

3(11 + x)

Since they covered the same distance, it means that

4x = 3(11 + x)

4x = 33 + 3x

4x - 3x = 33

x = 33 mph