City K and City L were 858 km apart. A sedan travelled from City K towards City L. At the same time, a lorry started from City L to City K. After travelling 1²₅ h, the two vehicles were still 585 km apart. If the ratio of the average speed of the lorry to that of the sedan was 6 : 7, find

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

(a)
Distance covered in 1²₅ h by the two vehicles
= 858 - 585
= 273 km

Combined speed of the two vehicles
= 273 ÷ ⁷₅
= 273 x ⁵₇
= 195 km/h

Average speed of the lorry : Average speed of the sedan = 6 : 7

6 u + 7 u = 13 u 
13 u = 195

1 u = 195 ÷ 13 = 15

Average speed of the sedan
= 7 u
= 7 x 15
= 105 km/h

(b)
Time taken for the lorry and the sedan to meet travelling the rest of the journey
= 585 ÷ 195
= 3 h 

Answer(s): (a) 105 km/h; (b) 3 h