City M and City N is 496 km apart. Neave left City M for City N at 7.00 a.m. travelling at an average speed of 62 km/h. Riordan left City M later than Neave and caught up with him at 10.00 a.m. Riordan was travelling at a speed of 72 km/h.

1. At what time did Riordan leave City M?
2. How much later did Neave arrive in City N than Riordan? 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 Neave covered when Riordan caught up with Neave
= 3 x 62
= 186 km

Time that Riordan took to travel 186 km
= 186 ÷ 72
= 2⁷₁₂ h

1 h = 60 min
⁷₁₂ h = ⁷₁₂ x 60 = 35 min
2⁷₁₂ h = 2 h 35 min

Time that Riordan left City M:
2 h 35 min before 10.00 a.m. = 7.25 a.m.

(b)
Remaining distance that they had to cover to reach City N
= 496 - 186
= 310 km

Duration that Riordan had to travel before reaching City N
= 310 ÷ 72
= 4¹¹₃₆ h

Duration that Neave had to travel before reaching City N
= 310 ÷ 62
= 5 h

Duration that Neave took to arrive later than Riordan in City N
= 5 - 4¹¹₃₆
= ²⁵₃₆ h

Answer(s): (a) 7.25 a.m.; (b) ²⁵₃₆ h