Sean and Tim took part in a 42 km marathon. Sean ran half the distance at a speed of 12 km/h and ran slower for the rest of the way at a speed of 7 km/h. Tim ran half his total time at 12 km/h and ran slower for the rest of the time at 6 km/h. If they started the marathon at 5.30 a.m., at what time would each of them finish?
- Sean
- Tim
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Sean for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Sean for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Sean
= 1
34 + 3
= 4
34 h
1 h = 60 min
34 h =
34 x 60 = 45 min
4
34 h = 4 h 45 min
4 h 45 min after 5.30 a.m. = 10.15 a.m.
Time that Sean would finish the marathon = 10.15 a.m.
(b)
Time taken by Tim for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Tim for the last half of the marathon
= 21 ÷ 6
= 3
12 h
Total time taken by Tim
= 1
34 + 3
12 = 5
14 h
1 h = 60 min
14 h =
14 x 60 = 15 min
5
14 h = 5 h 15 min
5 h 15 min after 5.30 a.m. = 10.45 a.m.
Time that Tim would finish the marathon = 10.45 a.m.
Answer(s): (a) 10.15 a.m.; (b) 10.45 a.m.