City W and City X were 243 km apart. A sports car travelled from City W towards City X. At the same time, a lorry started from City X to City W. After travelling 1
14 h, the two vehicles were still 108 km apart. If the ratio of the average speed of the lorry to that of the sports car was 4 : 5, find
- the average speed of the sports car.
- the time taken for them to meet travelling the rest of the journey. Express your answer in h.
(a)
Distance covered in 1
14 h by the two vehicles
= 243 - 108
= 135 km
Combined speed of the two vehicles
= 135 ÷
54 = 135 x
45 = 108 km/h
Average speed of the lorry : Average speed of the sports car = 4 : 5
4 u + 5 u = 9 u
9 u = 108
1 u = 108 ÷ 9 = 12
Average speed of the sports car
= 5 u
= 5 x 12
= 60 km/h
(b)
Time taken for the lorry and the sports car to meet travelling the rest of the journey
= 108 ÷ 108
= 1 h
Answer(s): (a) 60 km/h; (b) 1 h