A man cycles from home to work at 15 km/h and returns at 20 km/h. If the next day he increases the speed of going by 5% and decreases the speed of coming by 10%, what is his average speed.
The man cycles from home to work at 15 km/h and returns at 20 km/h.
If the speed of going is increased by 5% an the speed at which he returns is decreased by 10%, the respective speeds are 15*(1+0.05) = 15.75 km/ h and 20*(1 - 0.1) = 18 km/h.
The average speed is now (15.75 + 18)/2 = 16.875 km/h