Xavier and Julian took part in a 42 km marathon. Xavier ran half the distance at a speed of 12 km/h and ran slower for the rest of the way at a speed of 7 km/h. Julian ran half his total time at 10 km/h and ran slower for the rest of the time at 7 km/h. If they started the marathon at 6.30 a.m., at what time would each of them finish?
- Xavier
- Julian
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Xavier for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Xavier for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Xavier
= 1
34 + 3
= 4
34 h
1 h = 60 min
34 h =
34 x 60 = 45 min
4
34 h = 4 h 45 min
4 h 45 min after 6.30 a.m. = 11.15 a.m.
Time that Xavier would finish the marathon = 11.15 a.m.
(b)
Time taken by Julian for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by Julian for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Julian
= 2
110 + 3
= 5
110 h
1 h = 60 min
110 h =
110 x 60 = 6 min
5
110 h = 5 h 6 min
5 h 6 min after 6.30 a.m. = 11.36 a.m.
Time that Julian would finish the marathon = 11.36 a.m.
Answer(s): (a) 11.15 a.m.; (b) 11.36 a.m.