City R and City S is 480 km apart. George left City R for City S at 9.00 a.m. travelling at an average speed of 60 km/h. Andy left City R later than George and caught up with him at 1.00 p.m. Andy was travelling at a speed of 90 km/h.

1. At what time did Andy leave City R?
2. How much later did George arrive in City S than Andy? Express your answer in h as a fraction or mixed number.

(a)
From 9.00 a.m. to 1.00 p.m. = 4 h

Distance that George covered when Andy caught up with George
= 4 x 60
= 240 km

Time that Andy took to travel 240 km
= 240 ÷ 90
= 2²₃ h

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

Time that Andy left City R:
2 h 40 min before 1.00 p.m. = 10.20 a.m.

(b)
Remaining distance that they had to cover to reach City S
= 480 - 240
= 240 km

Duration that Andy had to travel before reaching City S
= 240 ÷ 90
= 2²₃ h

Duration that George had to travel before reaching City S
= 240 ÷ 60
= 4 h

Duration that George took to arrive later than Andy in City S
= 4 - 2²₃
= 1¹₃ h

Answer(s): (a) 10.20 a.m.; (b) 1¹₃ h