City F and City G is 320 km apart. Tommy left City F for City G at 8.00 a.m. travelling at an average speed of 64 km/h. Mark left City F later than Tommy and caught up with him at 11.00 a.m. Mark was travelling at a speed of 72 km/h.

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

(a)
From 8.00 a.m. to 11.00 a.m. = 3 h

Distance that Tommy covered when Mark caught up with Tommy
= 3 x 64
= 192 km

Time that Mark took to travel 192 km
= 192 ÷ 72
= 2²₃ h

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

Time that Mark left City F:
2 h 40 min before 11.00 a.m. = 8.20 a.m.

(b)
Remaining distance that they had to cover to reach City G
= 320 - 192
= 128 km

Duration that Mark had to travel before reaching City G
= 128 ÷ 72
= 1⁷₉ h

Duration that Tommy had to travel before reaching City G
= 128 ÷ 64
= 2 h

Duration that Tommy took to arrive later than Mark in City G
= 2 - 1⁷₉
= ²₉ h

Answer(s): (a) 8.20 a.m.; (b) ²₉ h