Charlie and Rael took part in a 32 km marathon. Charlie ran half the distance at a speed of 8 km/h and ran slower for the rest of the way at a speed of 6 km/h. Rael ran half his total time at 12 km/h and ran slower for the rest of the time at 8 km/h. If they started the marathon at 5.30 a.m., at what time would each of them finish?
- Charlie
- Rael
(a)
Half of the 32 km marathon = 32 ÷ 2 = 16 km
Time taken by Charlie for the first half of the marathon
= 16 ÷ 8
= 2 h
Time taken by Charlie for the last half of the marathon
= 16 ÷ 6
= 2
23 h
Total time taken by Charlie
= 2 + 2
23= 4
23 h
1 h = 60 min
23 h =
23 x 60 = 40 min
4
23 h = 4 h 40 min
4 h 40 min after 5.30 a.m. = 10.10 a.m.
Time that Charlie would finish the marathon = 10.10 a.m.
(b)
Time taken by Rael for the first half of the marathon
= 16 ÷ 12
= 1
13 h
Time taken by Rael for the last half of the marathon
= 16 ÷ 8
= 2 h
Total time taken by Rael
= 1
13 + 2
= 3
13 h
1 h = 60 min
13 h =
13 x 60 = 20 min
3
13 h = 3 h 20 min
3 h 20 min after 5.30 a.m. = 8.50 a.m.
Time that Rael would finish the marathon = 8.50 a.m.
Answer(s): (a) 10.10 a.m.; (b) 8.50 a.m.