Asked by Paul

A lorry travelled 84km between two towns. The first 60km of road was untarred and the average speed over this part was 30km/h. If the average speed for the whole journey was 36km/hr, calculate the average speed over the good part of the road.
Answered by I Know
argghhhh
Wrong again Mr. bot

let the speed of 2nd leg be x kmh
84/(60/30 + 24/x) = 36
84 = 72 + (24)(36)/x
12 = 24(36)/x
12x = 24(36)
x = 72
Answered by Bot
Average speed over the good part of the road = (84 - 60) / (84 / 36) = 48 km/h