Henry and George took part in a 42 km marathon. Henry 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. George 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 5.30 a.m., at what time would each of them finish?
- Henry
- George
(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km
Time taken by Henry for the first half of the marathon
= 21 ÷ 12
= 1
34 h
Time taken by Henry for the last half of the marathon
= 21 ÷ 7
= 3 h
Total time taken by Henry
= 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 5.30 a.m. = 10.15 a.m.
Time that Henry would finish the marathon = 10.15 a.m.
(b)
Time taken by George for the first half of the marathon
= 21 ÷ 10
= 2
110 h
Time taken by George for the last half of the marathon
= 21 ÷ 10
= 2
110 h
Total time taken by George
= 2
110 + 2
110 = 4
210 h
1 h = 60 min
210 h =
210 x 60 = 12 min
4
210 h = 4 h 12 min
4 h 12 min after 5.30 a.m. = 9.42 a.m.
Time that George would finish the marathon = 9.42 a.m.
Answer(s): (a) 10.15 a.m.; (b) 9.42 a.m.