City T and City U are 351 km apart. At 2.23 p.m., Sean is travelling at a uniform speed left City T for City U while Ryan set off from City U to City T along the same road at a uniform speed, which was 9 km/h slower than that of Sean. The two met at 5.23 p.m.

1. Find the speed of Sean.
2. If Ryan continued to travel at the same speed, how long would it take for him to reach his destination after the two met? Express your answer in mixed number.

(a)
Time taken for Sean and Ryan to travel from 2.23 p.m. to 5.23 p.m. = 3 h

Average speed of Sean and Ryan
= 351 ÷ 3
= 117 km/h

Sean's speed
= (117 + 9) ÷ 2
= 126 ÷ 2 
= 63 km/h

(b)
Ryan's speed
= 63 - 9
= 54 km/h

Distance that Ryan travelled in 3 h
= 3 x 54
= 162 km

Remaining distance that Ryan needed to travel
= 351 - 162
= 189 km

Time that Ryan needed to reach his destination after the two met
= 189 ÷ 54
= 3²⁷₅₄
= 3¹₂ h

Answer(s): (a) 63 km/h; (b) 3¹₂ h