A lorry and a Lamborghini started travelling from Town W to Town X at the same time. After 4 hours, the Lamborghini reached Town X while the lorry covered only ⁷₉ of the journey. The speed of the Lamborghini was 18 km/h more than the speed of the lorry. Find the speed of the lorry.
Extra distance covered by the Lamborghini in 4 h
= 4 x 18
= 72 km

When the Lamborghini reached Town X:
Distance covered by the Lamborghini = 9 u
Distance covered by the lorry = 7 u

Extra distance covered by the Lamborghini 
= 9 u - 7 u
= 2 u

2 u = 72

1 u = 72 ÷ 2 = 36

Distance covered by the lorry when the Lamborghini reached Town X
= 7 u
= 7 x 36
= 252 km

Speed of the lorry
= 252 ÷ 4
= 63 km/h

Answer(s): 63 km/h