Oliver and Ryan took part in a 24 km marathon. Oliver 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. Ryan 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 3.30 a.m., at what time would each of them finish?
- Oliver
- Ryan
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Oliver for the first half of the marathon
= 12 ÷ 8
= 1
12 h
Time taken by Oliver for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Oliver
= 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 3.30 a.m. = 7.24 a.m.
Time that Oliver would finish the marathon = 7.24 a.m.
(b)
Time taken by Ryan for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by Ryan for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by Ryan
= 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 3.30 a.m. = 5.50 a.m.
Time that Ryan would finish the marathon = 5.50 a.m.
Answer(s): (a) 7.24 a.m.; (b) 5.50 a.m.