City R and City S is 315 km apart. Warren left City R for City S at 7.00 a.m. travelling at an average speed of 63 km/h. David left City R later than Warren and caught up with him at 10.00 a.m. David was travelling at a speed of 81 km/h.

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

(a)
From 7.00 a.m. to 10.00 a.m. = 3 h

Distance that Warren covered when David caught up with Warren
= 3 x 63
= 189 km

Time that David took to travel 189 km
= 189 ÷ 81
= 2¹₃ h

1 h = 60 min
¹₃ h = ¹₃ x 60 = 20 min
2¹₃ h = 2 h 20 min

Time that David left City R:
2 h 20 min before 10.00 a.m. = 7.40 a.m.

(b)
Remaining distance that they had to cover to reach City S
= 315 - 189
= 126 km

Duration that David had to travel before reaching City S
= 126 ÷ 81
= 1⁵₉ h

Duration that Warren had to travel before reaching City S
= 126 ÷ 63
= 2 h

Duration that Warren took to arrive later than David in City S
= 2 - 1⁵₉
= ⁴₉ h

Answer(s): (a) 7.40 a.m.; (b) ⁴₉ h