Will and Bobby took part in a 24 km marathon. Will ran half the distance at a speed of 10 km/h and ran slower for the rest of the way at a speed of 8 km/h. Bobby ran half his total time at 12 km/h and ran slower for the rest of the time at 5 km/h. If they started the marathon at 4.30 a.m., at what time would each of them finish?
- Will
- Bobby
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Will for the first half of the marathon
= 12 ÷ 10
= 1
15 h
Time taken by Will for the last half of the marathon
= 12 ÷ 8
= 1
12 h
Total time taken by Will
= 1
15 + 1
12= 2
710 h
1 h = 60 min
710 h =
710 x 60 = 42 min
2
710 h = 2 h 42 min
2 h 42 min after 4.30 a.m. = 7.12 a.m.
Time that Will would finish the marathon = 7.12 a.m.
(b)
Time taken by Bobby for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by Bobby for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Bobby
= 1 + 2
25 = 3
25 h
1 h = 60 min
25 h =
25 x 60 = 24 min
3
25 h = 3 h 24 min
3 h 24 min after 4.30 a.m. = 7.54 a.m.
Time that Bobby would finish the marathon = 7.54 a.m.
Answer(s): (a) 7.12 a.m.; (b) 7.54 a.m.