Will and Fred took part in a 42 km marathon. Will ran half the distance at a speed of 12 km/h and ran slower for the rest of the way at a speed of 5 km/h. Fred 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?
- Will
- Fred
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Will for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Will for the last half of the marathon
= 21 ÷ 5
= 4
15 h
Total time taken by Will
= 1
34 + 4
15= 5
1920 h
1 h = 60 min
1920 h =
1920 x 60 = 57 min
5
1920 h = 5 h 57 min
5 h 57 min after 3.30 a.m. = 9.27 a.m.
Time that Will would finish the marathon = 9.27 a.m.
(b)
Time taken by Fred for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Fred for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Fred
= 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 Fred would finish the marathon = 8.36 a.m.
Answer(s): (a) 9.27 a.m.; (b) 8.36 a.m.