Charlie and Zane took part in a 42 km marathon. Charlie ran half the distance at a speed of 12 km/h and ran slower for the rest of the way at a speed of 7 km/h. Zane ran half his total time at 10 km/h and ran slower for the rest of the time at 9 km/h. If they started the marathon at 6.30 a.m., at what time would each of them finish?
- Charlie
- Zane
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Charlie for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Charlie for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Charlie
= 1
34 + 3
= 4
34 h
1 h = 60 min
34 h =
34 x 60 = 45 min
4
34 h = 4 h 45 min
4 h 45 min after 6.30 a.m. = 11.15 a.m.
Time that Charlie would finish the marathon = 11.15 a.m.
(b)
Time taken by Zane for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Zane for the last half of the marathon
= 21 ÷ 9
= 2
13 h
Total time taken by Zane
= 2
110 + 2
13 = 4
1330 h
1 h = 60 min
1330 h =
1330 x 60 = 26 min
4
1330 h = 4 h 26 min
4 h 26 min after 6.30 a.m. = 10.56 a.m.
Time that Zane would finish the marathon = 10.56 a.m.
Answer(s): (a) 11.15 a.m.; (b) 10.56 a.m.