City Y and City Z are 360 km apart. At 5.59 p.m., Ben is travelling at a uniform speed left City Y for City Z while Sean set off from City Z to City Y along the same road at a uniform speed, which was 6 km/h slower than that of Ben. The two met at 8.59 p.m.

1. Find the speed of Ben.
2. If Sean 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 Ben and Sean to travel from 5.59 p.m. to 8.59 p.m. = 3 h

Average speed of Ben and Sean
= 360 ÷ 3
= 120 km/h

Ben's speed
= (120 + 6) ÷ 2
= 126 ÷ 2 
= 63 km/h

(b)
Sean's speed
= 63 - 6
= 57 km/h

Distance that Sean travelled in 3 h
= 3 x 57
= 171 km

Remaining distance that Sean needed to travel
= 360 - 171
= 189 km

Time that Sean needed to reach his destination after the two met
= 189 ÷ 57
= 3¹⁸₅₇
= 3⁶₁₉ h

Answer(s): (a) 63 km/h; (b) 3⁶₁₉ h