Sam was still finishing his breakfast when his brother Leo left for school. Sam started to run after Leo when Leo was already 100 meters away. How soon will Sam catch up, if he is running at a speed of 105 meters per minute while Leo is walking at a speed of 65 meters per minute?

The answer to this question would be: 2.5 minute

In this question, when Sam started to run Leo was already 100 meters away. But Sam runs 105m/min which was faster than Leo (65m/min).

Then the time needed for Sam to catch up Leo should be:

time = distance / (Sam speed-Leos peed)

time = 100m / (105-65m/min)

time = 100m / (40m/min) = 2.5min