City Z and City A is 414 km apart. Zeph left City Z for City A at 7.00 a.m. travelling at an average speed of 69 km/h. Bobby left City Z later than Zeph and caught up with him at 9.00 a.m. Bobby was travelling at a speed of 72 km/h.

1. At what time did Bobby leave City Z?
2. How much later did Zeph arrive in City A than Bobby? 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 Zeph covered when Bobby caught up with Zeph
= 2 x 69
= 138 km

Time that Bobby took to travel 138 km
= 138 ÷ 72
= 1¹¹₁₂ h

1 h = 60 min
¹¹₁₂ h = ¹¹₁₂ x 60 = 55 min
1¹¹₁₂ h = 1 h 55 min

Time that Bobby left City Z:
1 h 55 min before 9.00 a.m. = 7.05 a.m.

(b)
Remaining distance that they had to cover to reach City A
= 414 - 138
= 276 km

Duration that Bobby had to travel before reaching City A
= 276 ÷ 72
= 3⁵₆ h

Duration that Zeph had to travel before reaching City A
= 276 ÷ 69
= 4 h

Duration that Zeph took to arrive later than Bobby in City A
= 4 - 3⁵₆
= ¹₆ h

Answer(s): (a) 7.05 a.m.; (b) ¹₆ h