Luis and Dylan took part in a 24 km marathon. Luis 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. Dylan ran half his total time at 12 km/h and ran slower for the rest of the time at 9 km/h. If they started the marathon at 5.30 a.m., at what time would each of them finish?
- Luis
- Dylan
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Luis for the first half of the marathon
= 12 ÷ 9
= 1
13 h
Time taken by Luis for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by Luis
= 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 5.30 a.m. = 8.10 a.m.
Time that Luis would finish the marathon = 8.10 a.m.
(b)
Time taken by Dylan for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by Dylan for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by Dylan
= 1 + 1
13 = 2
13 h
1 h = 60 min
13 h =
13 x 60 = 20 min
2
13 h = 2 h 20 min
2 h 20 min after 5.30 a.m. = 7.50 a.m.
Time that Dylan would finish the marathon = 7.50 a.m.
Answer(s): (a) 8.10 a.m.; (b) 7.50 a.m.