City M and City N are 564 km apart. At 4.36 p.m., Luis is travelling at a uniform speed left City M for City N while Charlie set off from City N to City M along the same road at a uniform speed, which was 5 km/h slower than that of Luis. The two met at 8.36 p.m.
- Find the speed of Luis.
- If Charlie 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 Luis and Charlie to travel from 4.36 p.m. to 8.36 p.m. = 4 h
Average speed of Luis and Charlie
= 564 ÷ 4
= 141 km/h
Luis's speed
= (141 + 5) ÷ 2
= 146 ÷ 2
= 73 km/h
(b)
Charlie's speed
= 73 - 5
= 68 km/h
Distance that Charlie travelled in 4 h
= 4 x 68
= 272 km
Remaining distance that Charlie needed to travel
= 564 - 272
= 292 km
Time that Charlie needed to reach his destination after the two met
= 292 ÷ 68
= 4
2068 = 4
517 h
Answer(s): (a) 73 km/h; (b) 4
517 h