City G and City H is 420 km apart. Ahmad left City G for City H at 7.00 a.m. travelling at an average speed of 70 km/h. Oliver left City G later than Ahmad and caught up with him at 9.00 a.m. Oliver was travelling at a speed of 105 km/h.

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

(a)
From 7.00 a.m. to 9.00 a.m. = 2 h

Distance that Ahmad covered when Oliver caught up with Ahmad
= 2 x 70
= 140 km

Time that Oliver took to travel 140 km
= 140 ÷ 105
= 1¹₃ h

1 h = 60 min
¹₃ h = ¹₃ x 60 = 20 min
1¹₃ h = 1 h 20 min

Time that Oliver left City G:
1 h 20 min before 9.00 a.m. = 7.40 a.m.

(b)
Remaining distance that they had to cover to reach City H
= 420 - 140
= 280 km

Duration that Oliver had to travel before reaching City H
= 280 ÷ 105
= 2²₃ h

Duration that Ahmad had to travel before reaching City H
= 280 ÷ 70
= 4 h

Duration that Ahmad took to arrive later than Oliver in City H
= 4 - 2²₃
= 1¹₃ h

Answer(s): (a) 7.40 a.m.; (b) 1¹₃ h