A man cycles from P to Q, a distance of 50 km, in 3 hours 36 minutes.  The road from P is a level road for 28 km and then it is uphill to Q.  The man's average speed on the level road is 20 km/h.  What is his average uphill speed (in km/h)?

10

Time taken to cover 28 km with speed of 20 km/h = \(\frac{28}{20}\) = 1 hour 24 minutes

Remaining time for travel 22 km = 3 h 36 min - 1 h 24 min

                                                   = 2 h 12 min

Uphill Speed = \(\frac{22}{2 h\;12 min}\) = \(\frac{22}{2 + \frac{1}{5}}\) = 10 km/h