Pierre and Zeph took part in a 24 km marathon. Pierre ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 5 km/h. Zeph ran half his total time at 10 km/h and ran slower for the rest of the time at 10 km/h. If they started the marathon at 5.30 a.m., at what time would each of them finish?
- Pierre
- Zeph
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Pierre for the first half of the marathon
= 12 ÷ 9
= 1
13 h
Time taken by Pierre for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Pierre
= 1
13 + 2
25= 3
1115 h
1 h = 60 min
1115 h =
1115 x 60 = 44 min
3
1115 h = 3 h 44 min
3 h 44 min after 5.30 a.m. = 9.14 a.m.
Time that Pierre would finish the marathon = 9.14 a.m.
(b)
Time taken by Zeph for the first half of the marathon
= 12 ÷ 10
= 1
15 h
Time taken by Zeph for the last half of the marathon
= 12 ÷ 10
= 1
15 h
Total time taken by Zeph
= 1
15 + 1
15 = 2
25 h
1 h = 60 min
25 h =
25 x 60 = 24 min
2
25 h = 2 h 24 min
2 h 24 min after 5.30 a.m. = 7.54 a.m.
Time that Zeph would finish the marathon = 7.54 a.m.
Answer(s): (a) 9.14 a.m.; (b) 7.54 a.m.