Mark and Ian took part in a 42 km marathon. Mark ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 6 km/h. Ian 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 4.30 a.m., at what time would each of them finish?
- Mark
- Ian
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Mark for the first half of the marathon
= 21 ÷ 9
= 2
13 h
Time taken by Mark for the last half of the marathon
= 21 ÷ 6
= 3
12 h
Total time taken by Mark
= 2
13 + 3
12= 5
56 h
1 h = 60 min
56 h =
56 x 60 = 50 min
5
56 h = 5 h 50 min
5 h 50 min after 4.30 a.m. = 10.20 a.m.
Time that Mark would finish the marathon = 10.20 a.m.
(b)
Time taken by Ian for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Ian for the last half of the marathon
= 21 ÷ 10
= 2
110 h
Total time taken by Ian
= 2
110 + 2
110 = 4
210 h
1 h = 60 min
210 h =
210 x 60 = 12 min
4
210 h = 4 h 12 min
4 h 12 min after 4.30 a.m. = 8.42 a.m.
Time that Ian would finish the marathon = 8.42 a.m.
Answer(s): (a) 10.20 a.m.; (b) 8.42 a.m.