Albert and Archie took part in a 42 km marathon. Albert 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. Archie ran half his total time at 10 km/h and ran slower for the rest of the time at 5 km/h. If they started the marathon at 6.30 a.m., at what time would each of them finish?

1. Albert
2. Archie

(a)
Half of the 42 km marathon = 42 ÷ 2 = 21 km

Time taken by Albert for the first half of the marathon
= 21 ÷ 9
= 2¹₃ h

Time taken by Albert for the last half of the marathon
= 21 ÷ 9
= 2¹₃ h

Total time taken by Albert
= 2¹₃ + 2¹₃
= 4²₃ h

1 h = 60 min
²₃ h = ²₃ x 60 = 40 min
4²₃ h = 4 h 40 min

4 h 40 min after 6.30 a.m. = 11.10 a.m.
Time that Albert would finish the marathon = 11.10 a.m.

(b)
Time taken by Archie for the first half of the marathon
= 21 ÷ 10
= 2¹₁₀ h

Time taken by Archie for the last half of the marathon
= 21 ÷ 5
= 4¹₅ h

Total time taken by Archie
= 2¹₁₀ + 4¹₅
= 6³₁₀ h

1 h = 60 min
³₁₀ h = ³₁₀ x 60 = 18 min
6³₁₀ h = 6 h 18 min
6 h 18 min after 6.30 a.m. = 12.48 a.m.
Time that Archie would finish the marathon = 12.48 a.m.

Answer(s): (a) 11.10 a.m.; (b) 12.48 a.m.