City R and City S were 315 km apart. A car travelled from City R towards City S. At the same time, a lorry started from City S to City R. After travelling 1¹₂ h, the two vehicles were still 126 km apart. If the ratio of the average speed of the lorry to that of the car was 4 : 5, find

1. the average speed of the car.
2. the time taken for them to meet travelling the rest of the journey. Express your answer in h.

(a)
Distance covered in 1¹₂ h by the two vehicles
= 315 - 126
= 189 km

Combined speed of the two vehicles
= 189 ÷ ³₂
= 189 x ²₃
= 126 km/h

Average speed of the lorry : Average speed of the car = 4 : 5

4 u + 5 u = 9 u 
9 u = 126

1 u = 126 ÷ 9 = 14

Average speed of the car
= 5 u
= 5 x 14
= 70 km/h

(b)
Time taken for the lorry and the car to meet travelling the rest of the journey
= 126 ÷ 126
= 1 h 

Answer(s): (a) 70 km/h; (b) 1 h