Ahmad and Rael took part in a 24 km marathon. Ahmad 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. Rael 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 3.30 a.m., at what time would each of them finish?
- Ahmad
- Rael
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Ahmad for the first half of the marathon
= 12 ÷ 10
= 1
15 h
Time taken by Ahmad for the last half of the marathon
= 12 ÷ 8
= 1
12 h
Total time taken by Ahmad
= 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 3.30 a.m. = 6.12 a.m.
Time that Ahmad would finish the marathon = 6.12 a.m.
(b)
Time taken by Rael for the first half of the marathon
= 12 ÷ 10
= 1
15 h
Time taken by Rael for the last half of the marathon
= 12 ÷ 10
= 1
15 h
Total time taken by Rael
= 1
15 + 1
15 = 2
25 h
1 h = 60 min
25 h =
25 x 60 = 24 min
2
25 h = 2 h 24 min
2 h 24 min after 3.30 a.m. = 5.54 a.m.
Time that Rael would finish the marathon = 5.54 a.m.
Answer(s): (a) 6.12 a.m.; (b) 5.54 a.m.