Question

a train travels 50 km in half hour. it the stops at a station for 20 mins, before traveling for 2 hours at an average speed of 90 km/h what was the trains average speed over the whole journey

Answer 1

The average speed

$$v_{\rm{ave}}=\frac{\rm{total\; distance}}{\rm{total\; time}}$$

$$v_{\rm{ave}}=\frac{50\:\rm{km}+0\:\rm{km}+180\:\rm{km}}{1/2\:\rm{hr}+1/3\:\rm{hr}+2\:\rm{hr}}$$

$$=81.2\:\rm{km/hr}$$