Average speed when distances are equal

A car travels at 60 mph on a trip and at 100 mph on return trip. What was its average speed for the entire trip? 
Solution: 

Total average speed = 2*60*100/(100+60) = 2*60*100/160 = 2*60*5/8 = 60*5/4 = 15*5 = 75 .

click below to see video trick when there are more than 2 equal distances.

1 Without stoppages a train travels a certain distance with an average speed of 50 kmph and with stoppages it covers the same distance with an average speed of 40 kmph. What is the time in minutes per hour for which train stops?

Without stoppages a train travels a certain distance with an average speed of 50 kmph and with stoppages it covers the same distance with an average speed of 40 kmph. What is the time in minutes per hour for which train stops?


For video solution of this question click below video