City Z and City A are 480 km apart. At 3.51 p.m., Mark is travelling at a uniform speed left City Z for City A while Ian set off from City A to City Z along the same road at a uniform speed, which was 12 km/h slower than that of Mark. The two met at 7.51 p.m.
- Find the speed of Mark.
- If Ian 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 Mark and Ian to travel from 3.51 p.m. to 7.51 p.m. = 4 h
Average speed of Mark and Ian
= 480 ÷ 4
= 120 km/h
Mark's speed
= (120 + 12) ÷ 2
= 132 ÷ 2
= 66 km/h
(b)
Ian's speed
= 66 - 12
= 54 km/h
Distance that Ian travelled in 4 h
= 4 x 54
= 216 km
Remaining distance that Ian needed to travel
= 480 - 216
= 264 km
Time that Ian needed to reach his destination after the two met
= 264 ÷ 54
= 4
4854 = 4
89 h
Answer(s): (a) 66 km/h; (b) 4
89 h