Ryan and John took part in a 24 km marathon. Ryan ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 5 km/h. John ran half his total time at 12 km/h and ran slower for the rest of the time at 9 km/h. If they started the marathon at 4.30 a.m., at what time would each of them finish?
- Ryan
- John
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Ryan for the first half of the marathon
= 12 ÷ 9
= 1
13 h
Time taken by Ryan for the last half of the marathon
= 12 ÷ 5
= 2
25 h
Total time taken by Ryan
= 1
13 + 2
25= 3
1115 h
1 h = 60 min
1115 h =
1115 x 60 = 44 min
3
1115 h = 3 h 44 min
3 h 44 min after 4.30 a.m. = 8.14 a.m.
Time that Ryan would finish the marathon = 8.14 a.m.
(b)
Time taken by John for the first half of the marathon
= 12 ÷ 12
= 1 h
Time taken by John for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by John
= 1 + 1
13 = 2
13 h
1 h = 60 min
13 h =
13 x 60 = 20 min
2
13 h = 2 h 20 min
2 h 20 min after 4.30 a.m. = 6.50 a.m.
Time that John would finish the marathon = 6.50 a.m.
Answer(s): (a) 8.14 a.m.; (b) 6.50 a.m.