City Z and City A were 624 km apart. A sedan 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 432 km apart. If the ratio of the average speed of the lorry to that of the sedan 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
= 624 - 432
= 192 km
Combined speed of the two vehicles
= 192 ÷
43 = 192 x
34 = 144 km/h
Average speed of the lorry : Average speed of the sedan = 4 : 5
4 u + 5 u = 9 u
9 u = 144
1 u = 144 ÷ 9 = 16
Average speed of the lorry
= 4 u
= 4 x 16
= 64 km/h
(b)
Time taken for the lorry and the sedan to meet travelling the rest of the journey
= 432 ÷ 144
= 3 h
Answer(s): (a) 64 km/h; (b) 3 h