City Z and City A were 420 km apart. A sports car travelled from City Z towards City A. At the same time, a lorry started from City A to City Z. After travelling 1
13 h, the two vehicles were still 252 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 lorry.
- the time taken for them to meet travelling the rest of the journey. Express your answer in h.
(a)
Distance covered in 1
13 h by the two vehicles
= 420 - 252
= 168 km
Combined speed of the two vehicles
= 168 ÷
43 = 168 x
34 = 126 km/h
Average speed of the lorry : Average speed of the sports car = 4 : 5
4 u + 5 u = 9 u
9 u = 126
1 u = 126 ÷ 9 = 14
Average speed of the lorry
= 4 u
= 4 x 14
= 56 km/h
(b)
Time taken for the lorry and the sports car to meet travelling the rest of the journey
= 252 ÷ 126
= 2 h
Answer(s): (a) 56 km/h; (b) 2 h