Henry and John took part in a 16 km marathon. Henry 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. John ran half his total time at 12 km/h and ran slower for the rest of the time at 5 km/h. If they started the marathon at 5.30 a.m., at what time would each of them finish?

1. Henry
2. John

(a)
Half of the 16 km marathon = 16 ÷ 2 = 8 km

Time taken by Henry for the first half of the marathon
= 8 ÷ 10
= ⁴₅ h

Time taken by Henry for the last half of the marathon
= 8 ÷ 8
= 1 h

Total time taken by Henry
= ⁴₅ + 1
= 1⁴₅ h

1 h = 60 min
⁴₅ h = ⁴₅ x 60 = 48 min
1⁴₅ h = 1 h 48 min

1 h 48 min after 5.30 a.m. = 7.18 a.m.
Time that Henry would finish the marathon = 7.18 a.m.

(b)
Time taken by John for the first half of the marathon
= 8 ÷ 12
= ²₃ h

Time taken by John for the last half of the marathon
= 8 ÷ 5
= 1³₅ h

Total time taken by John
= ²₃ + 1³₅
= 2⁴₁₅ h

1 h = 60 min
⁴₁₅ h = ⁴₁₅ x 60 = 16 min
2⁴₁₅ h = 2 h 16 min
2 h 16 min after 5.30 a.m. = 7.46 a.m.
Time that John would finish the marathon = 7.46 a.m.

Answer(s): (a) 7.18 a.m.; (b) 7.46 a.m.