Elijah and Lee took part in a 42 km marathon. Elijah 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. Lee 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 4.30 a.m., at what time would each of them finish?
- Elijah
- Lee
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Elijah for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Elijah for the last half of the marathon
= 21 ÷ 5
= 4
15 h
Total time taken by Elijah
= 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 4.30 a.m. = 10.27 a.m.
Time that Elijah would finish the marathon = 10.27 a.m.
(b)
Time taken by Lee for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Lee for the last half of the marathon
= 21 ÷ 6
= 3
12 h
Total time taken by Lee
= 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 4.30 a.m. = 9.45 a.m.
Time that Lee would finish the marathon = 9.45 a.m.
Answer(s): (a) 10.27 a.m.; (b) 9.45 a.m.