Henry and Michael took part in a 24 km marathon. Henry ran half the distance at a speed of 9 km/h and ran slower for the rest of the way at a speed of 9 km/h. Michael 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?
- Henry
- Michael
(a)
Half of the 24 km marathon = 24 ÷ 2 = 12 km
Time taken by Henry for the first half of the marathon
= 12 ÷ 9
= 1
13 h
Time taken by Henry for the last half of the marathon
= 12 ÷ 9
= 1
13 h
Total time taken by Henry
= 1
13 + 1
13= 2
23 h
1 h = 60 min
23 h =
23 x 60 = 40 min
2
23 h = 2 h 40 min
2 h 40 min after 4.30 a.m. = 7.10 a.m.
Time that Henry would finish the marathon = 7.10 a.m.
(b)
Time taken by Michael for the first half of the marathon
= 12 ÷ 10
= 1
15 h
Time taken by Michael for the last half of the marathon
= 12 ÷ 10
= 1
15 h
Total time taken by Michael
= 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 4.30 a.m. = 6.54 a.m.
Time that Michael would finish the marathon = 6.54 a.m.
Answer(s): (a) 7.10 a.m.; (b) 6.54 a.m.