Mark and Warren took part in a 42 km marathon. Mark 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. Warren ran half his total time at 10 km/h and ran slower for the rest of the time at 9 km/h. If they started the marathon at 6.30 a.m., at what time would each of them finish?
- Mark
- Warren
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Mark for the first half of the marathon
= 21 ÷ 9
= 2
13 h
Time taken by Mark for the last half of the marathon
= 21 ÷ 9
= 2
13 h
Total time taken by Mark
= 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 6.30 a.m. = 11.10 a.m.
Time that Mark would finish the marathon = 11.10 a.m.
(b)
Time taken by Warren for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Warren for the last half of the marathon
= 21 ÷ 9
= 2
13 h
Total time taken by Warren
= 2
110 + 2
13 = 4
1330 h
1 h = 60 min
1330 h =
1330 x 60 = 26 min
4
1330 h = 4 h 26 min
4 h 26 min after 6.30 a.m. = 10.56 a.m.
Time that Warren would finish the marathon = 10.56 a.m.
Answer(s): (a) 11.10 a.m.; (b) 10.56 a.m.