City R and City S are 500 km apart. At 5.24 p.m., David is travelling at a uniform speed left City R for City S while Riordan set off from City S to City R along the same road at a uniform speed, which was 5 km/h slower than that of David. The two met at 9.24 p.m.
- Find the speed of David.
- If Riordan 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 David and Riordan to travel from 5.24 p.m. to 9.24 p.m. = 4 h
Average speed of David and Riordan
= 500 ÷ 4
= 125 km/h
David's speed
= (125 + 5) ÷ 2
= 130 ÷ 2
= 65 km/h
(b)
Riordan's speed
= 65 - 5
= 60 km/h
Distance that Riordan travelled in 4 h
= 4 x 60
= 240 km
Remaining distance that Riordan needed to travel
= 500 - 240
= 260 km
Time that Riordan needed to reach his destination after the two met
= 260 ÷ 60
= 4
2060 = 4
13 h
Answer(s): (a) 65 km/h; (b) 4
13 h