Charlie and Luis took part in a 42 km marathon. Charlie ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 6 km/h. Luis ran half his total time at 10 km/h and ran slower for the rest of the time at 7 km/h. If they started the marathon at 3.30 a.m., at what time would each of them finish?
- Charlie
- Luis
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Charlie for the first half of the marathon
= 21 ÷ 9
= 2
13 h
Time taken by Charlie for the last half of the marathon
= 21 ÷ 6
= 3
12 h
Total time taken by Charlie
= 2
13 + 3
12= 5
56 h
1 h = 60 min
56 h =
56 x 60 = 50 min
5
56 h = 5 h 50 min
5 h 50 min after 3.30 a.m. = 9.20 a.m.
Time that Charlie would finish the marathon = 9.20 a.m.
(b)
Time taken by Luis for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Luis for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Luis
= 2
110 + 3
= 5
110 h
1 h = 60 min
110 h =
110 x 60 = 6 min
5
110 h = 5 h 6 min
5 h 6 min after 3.30 a.m. = 8.36 a.m.
Time that Luis would finish the marathon = 8.36 a.m.
Answer(s): (a) 9.20 a.m.; (b) 8.36 a.m.