City D and City E is 456 km apart. Mark left City D for City E at 7.00 a.m. travelling at an average speed of 76 km/h. Sean left City D later than Mark and caught up with him at 9.00 a.m. Sean was travelling at a speed of 114 km/h.

1. At what time did Sean leave City D?
2. How much later did Mark arrive in City E than Sean? 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 Mark covered when Sean caught up with Mark
= 2 x 76
= 152 km

Time that Sean took to travel 152 km
= 152 ÷ 114
= 1¹₃ h

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

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

(b)
Remaining distance that they had to cover to reach City E
= 456 - 152
= 304 km

Duration that Sean had to travel before reaching City E
= 304 ÷ 114
= 2²₃ h

Duration that Mark had to travel before reaching City E
= 304 ÷ 76
= 4 h

Duration that Mark took to arrive later than Sean in City E
= 4 - 2²₃
= 1¹₃ h

Answer(s): (a) 7.40 a.m.; (b) 1¹₃ h