City H and City J are 570 km apart. At 5.24 p.m., Charlie is travelling at a uniform speed left City H for City J while Henry set off from City J to City H along the same road at a uniform speed, which was 12 km/h slower than that of Charlie. The two met at 10.24 p.m.

1. Find the speed of Charlie.
2. If Henry continued to travel at the same speed, how long would it take for him to reach his destination after the two met? Express your answer in mixed number.

(a)
Time taken for Charlie and Henry to travel from 5.24 p.m. to 10.24 p.m. = 5 h

Average speed of Charlie and Henry
= 570 ÷ 5
= 114 km/h

Charlie's speed
= (114 + 12) ÷ 2
= 126 ÷ 2 
= 63 km/h

(b)
Henry's speed
= 63 - 12
= 51 km/h

Distance that Henry travelled in 5 h
= 5 x 51
= 255 km

Remaining distance that Henry needed to travel
= 570 - 255
= 315 km

Time that Henry needed to reach his destination after the two met
= 315 ÷ 51
= 6⁹₅₁
= 6³₁₇ h

Answer(s): (a) 63 km/h; (b) 6³₁₇ h