A man cycles from P to Q, a distance of 30 km, in 2 hours 48 minutes. The road from P is a level road for 18 km and then it is uphill to Q. The man's average speed on the level road is 15 km/h. What is his average uphill speed (in km/h)?

7.5

Total distance = 30 km , Total time = 2 hours 48 minutes = 2.8 hours

Time to travel 18km level road = \(\frac{18}{15}\) = 1.2 hours

Uphill distance = 30 - 18 = 12 km

Remaining time to travel uphill = 2.8 - 1.2 =1.6 hours

Speed to travel uphill = \(\frac{12}{1.6}\) = 75 km/h

So, Average uphill speed = 75 km/h