Rael and Perry took part in a 24 km marathon. Rael ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 9 km/h. Perry ran half his total time at 12 km/h and ran slower for the rest of the time at 10 km/h. If they started the marathon at 7.30 a.m., at what time would each of them finish?
- Rael
- Perry
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Rael for the first half of the marathon
= 12 ÷ 9
= 1
13 h
Time taken by Rael for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by Rael
= 1
13 + 1
13= 2
23 h
1 h = 60 min
23 h =
23 x 60 = 40 min
2
23 h = 2 h 40 min
2 h 40 min after 7.30 a.m. = 10.10 a.m.
Time that Rael would finish the marathon = 10.10 a.m.
(b)
Time taken by Perry for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by Perry for the last half of the marathon
= 12 ÷ 10
= 1
15 h
Total time taken by Perry
= 1 + 1
15 = 2
15 h
1 h = 60 min
15 h =
15 x 60 = 12 min
2
15 h = 2 h 12 min
2 h 12 min after 7.30 a.m. = 9.42 a.m.
Time that Perry would finish the marathon = 9.42 a.m.
Answer(s): (a) 10.10 a.m.; (b) 9.42 a.m.