Luis and Oscar took part in a 24 km marathon. Luis ran half the distance at a speed of 8 km/h and ran slower for the rest of the way at a speed of 5 km/h. Oscar ran half his total time at 12 km/h and ran slower for the rest of the time at 5 km/h. If they started the marathon at 7.30 a.m., at what time would each of them finish?
- Luis
- Oscar
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Luis for the first half of the marathon
= 12 ÷ 8
= 1
12 h
Time taken by Luis for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Luis
= 1
12 + 2
25= 3
910 h
1 h = 60 min
910 h =
910 x 60 = 54 min
3
910 h = 3 h 54 min
3 h 54 min after 7.30 a.m. = 11.24 a.m.
Time that Luis would finish the marathon = 11.24 a.m.
(b)
Time taken by Oscar for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by Oscar for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Oscar
= 1 + 2
25 = 3
25 h
1 h = 60 min
25 h =
25 x 60 = 24 min
3
25 h = 3 h 24 min
3 h 24 min after 7.30 a.m. = 10.54 a.m.
Time that Oscar would finish the marathon = 10.54 a.m.
Answer(s): (a) 11.24 a.m.; (b) 10.54 a.m.