Billy and Howard took part in a 16 km marathon. Billy ran half the distance at a speed of 10 km/h and ran slower for the rest of the way at a speed of 8 km/h. Howard ran half his total time at 12 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?
- Billy
- Howard
(a)
Half of the 16 km marathon = 16 ÷ 2 = 8 km
Time taken by Billy for the first half of the marathon
= 8 ÷ 10
=
45 h
Time taken by Billy for the last half of the marathon
= 8 ÷ 8
= 1 h
Total time taken by Billy
=
45 + 1
= 1
45 h
1 h = 60 min
45 h =
45 x 60 = 48 min
1
45 h = 1 h 48 min
1 h 48 min after 4.30 a.m. = 6.18 a.m.
Time that Billy would finish the marathon = 6.18 a.m.
(b)
Time taken by Howard for the first half of the marathon
= 8 ÷ 12
=
23 h
Time taken by Howard for the last half of the marathon
= 8 ÷ 10
=
45 h
Total time taken by Howard
=
23 +
45 = 1
715 h
1 h = 60 min
715 h =
715 x 60 = 28 min
1
715 h = 1 h 28 min
1 h 28 min after 4.30 a.m. = 5.58 a.m.
Time that Howard would finish the marathon = 5.58 a.m.
Answer(s): (a) 6.18 a.m.; (b) 5.58 a.m.