City G and City H is 300 km apart. Charlie left City G for City H at 7.00 a.m. travelling at an average speed of 60 km/h. Vaidev left City G later than Charlie and caught up with him at 9.00 a.m. Vaidev was travelling at a speed of 72 km/h.

1. At what time did Vaidev leave City G?
2. How much later did Charlie arrive in City H than Vaidev? 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 Charlie covered when Vaidev caught up with Charlie
= 2 x 60
= 120 km

Time that Vaidev took to travel 120 km
= 120 ÷ 72
= 1²₃ h

1 h = 60 min
²₃ h = ²₃ x 60 = 40 min
1²₃ h = 1 h 40 min

Time that Vaidev left City G:
1 h 40 min before 9.00 a.m. = 7.20 a.m.

(b)
Remaining distance that they had to cover to reach City H
= 300 - 120
= 180 km

Duration that Vaidev had to travel before reaching City H
= 180 ÷ 72
= 2¹₂ h

Duration that Charlie had to travel before reaching City H
= 180 ÷ 60
= 3 h

Duration that Charlie took to arrive later than Vaidev in City H
= 3 - 2¹₂
= ¹₂ h

Answer(s): (a) 7.20 a.m.; (b) ¹₂ h