City H and City J is 624 km apart. Vincent left City H for City J at 8.00 a.m. travelling at an average speed of 78 km/h. Harry left City H later than Vincent and caught up with him at 12.00 p.m. Harry was travelling at a speed of 117 km/h.

1. At what time did Harry leave City H?
2. How much later did Vincent arrive in City J than Harry? Express your answer in h as a fraction or mixed number.

(a)
From 8.00 a.m. to 12.00 p.m. = 4 h

Distance that Vincent covered when Harry caught up with Vincent
= 4 x 78
= 312 km

Time that Harry took to travel 312 km
= 312 ÷ 117
= 2²₃ h

1 h = 60 min
²₃ h = ²₃ x 60 = 40 min
2²₃ h = 2 h 40 min

Time that Harry left City H:
2 h 40 min before 12.00 p.m. = 9.20 a.m.

(b)
Remaining distance that they had to cover to reach City J
= 624 - 312
= 312 km

Duration that Harry had to travel before reaching City J
= 312 ÷ 117
= 2²₃ h

Duration that Vincent had to travel before reaching City J
= 312 ÷ 78
= 4 h

Duration that Vincent took to arrive later than Harry in City J
= 4 - 2²₃
= 1¹₃ h

Answer(s): (a) 9.20 a.m.; (b) 1¹₃ h