City B and City C are 402 km apart. At 6.11 p.m., Vaidev is travelling at a uniform speed left City B for City C while David set off from City C to City B along the same road at a uniform speed, which was 8 km/h slower than that of Vaidev. The two met at 9.11 p.m.
- Find the speed of Vaidev.
- If David 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 Vaidev and David to travel from 6.11 p.m. to 9.11 p.m. = 3 h
Average speed of Vaidev and David
= 402 ÷ 3
= 134 km/h
Vaidev's speed
= (134 + 8) ÷ 2
= 142 ÷ 2
= 71 km/h
(b)
David's speed
= 71 - 8
= 63 km/h
Distance that David travelled in 3 h
= 3 x 63
= 189 km
Remaining distance that David needed to travel
= 402 - 189
= 213 km
Time that David needed to reach his destination after the two met
= 213 ÷ 63
= 3
2463 = 3
821 h
Answer(s): (a) 71 km/h; (b) 3
821 h