City L and City M were 726 km apart. A sports car travelled from City L towards City M. At the same time, a lorry started from City M to City L. After travelling 1
25 h, the two vehicles were still 495 km apart. If the ratio of the average speed of the lorry to that of the sports car was 5 : 6, 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
25 h by the two vehicles
= 726 - 495
= 231 km
Combined speed of the two vehicles
= 231 ÷
75 = 231 x
57 = 165 km/h
Average speed of the lorry : Average speed of the sports car = 5 : 6
5 u + 6 u = 11 u
11 u = 165
1 u = 165 ÷ 11 = 15
Average speed of the lorry
= 5 u
= 5 x 15
= 75 km/h
(b)
Time taken for the lorry and the sports car to meet travelling the rest of the journey
= 495 ÷ 165
= 3 h
Answer(s): (a) 75 km/h; (b) 3 h