Daniel and Perry took part in a 42 km marathon. Daniel 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. Perry 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 7.30 a.m., at what time would each of them finish?
- Daniel
- Perry
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Daniel for the first half of the marathon
= 21 ÷ 9
= 2
13 h
Time taken by Daniel for the last half of the marathon
= 21 ÷ 9
= 2
13 h
Total time taken by Daniel
= 2
13 + 2
13= 4
23 h
1 h = 60 min
23 h =
23 x 60 = 40 min
4
23 h = 4 h 40 min
4 h 40 min after 7.30 a.m. = 12.10 a.m.
Time that Daniel would finish the marathon = 12.10 a.m.
(b)
Time taken by Perry for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Perry for the last half of the marathon
= 21 ÷ 9
= 2
13 h
Total time taken by Perry
= 1
34 + 2
13 = 4
112 h
1 h = 60 min
112 h =
112 x 60 = 5 min
4
112 h = 4 h 5 min
4 h 5 min after 7.30 a.m. = 11.35 a.m.
Time that Perry would finish the marathon = 11.35 a.m.
Answer(s): (a) 12.10 a.m.; (b) 11.35 a.m.