City F and City G is 360 km apart. Pierre left City F for City G at 7.00 a.m. travelling at an average speed of 60 km/h. Henry left City F later than Pierre and caught up with him at 9.00 a.m. Henry was travelling at a speed of 72 km/h.

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

(a)
From 7.00 a.m. to 9.00 a.m. = 2 h

Distance that Pierre covered when Henry caught up with Pierre
= 2 x 60
= 120 km

Time that Henry took to travel 120 km
= 120 ÷ 72
= 1²₃ h

1 h = 60 min
²₃ h = ²₃ x 60 = 40 min
1²₃ h = 1 h 40 min

Time that Henry left City F:
1 h 40 min before 9.00 a.m. = 7.20 a.m.

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

Duration that Henry had to travel before reaching City G
= 240 ÷ 72
= 3¹₃ h

Duration that Pierre had to travel before reaching City G
= 240 ÷ 60
= 4 h

Duration that Pierre took to arrive later than Henry in City G
= 4 - 3¹₃
= ²₃ h

Answer(s): (a) 7.20 a.m.; (b) ²₃ h