City Z and City A is 360 km apart. Albert left City Z for City A at 7.00 a.m. travelling at an average speed of 60 km/h. Julian left City Z later than Albert and caught up with him at 11.00 a.m. Julian was travelling at a speed of 90 km/h.

1. At what time did Julian leave City Z?
2. How much later did Albert arrive in City A than Julian? Express your answer in h as a fraction or mixed number.

(a)
From 7.00 a.m. to 11.00 a.m. = 4 h

Distance that Albert covered when Julian caught up with Albert
= 4 x 60
= 240 km

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

(b)
Remaining distance that they had to cover to reach City A
= 360 - 240
= 120 km

Duration that Julian had to travel before reaching City A
= 120 ÷ 90
= 1¹₃ h

Duration that Albert had to travel before reaching City A
= 120 ÷ 60
= 2 h

Duration that Albert took to arrive later than Julian in City A
= 2 - 1¹₃
= ²₃ h

Answer(s): (a) 8.20 a.m.; (b) ²₃ h