City J and City K are 484 km apart. At 1.14 p.m., David is travelling at a uniform speed left City J for City K while Justin set off from City K to City J along the same road at a uniform speed, which was 11 km/h slower than that of David. The two met at 5.14 p.m.

1. Find the speed of David.
2. If Justin 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 David and Justin to travel from 1.14 p.m. to 5.14 p.m. = 4 h

Average speed of David and Justin
= 484 ÷ 4
= 121 km/h

David's speed
= (121 + 11) ÷ 2
= 132 ÷ 2 
= 66 km/h

(b)
Justin's speed
= 66 - 11
= 55 km/h

Distance that Justin travelled in 4 h
= 4 x 55
= 220 km

Remaining distance that Justin needed to travel
= 484 - 220
= 264 km

Time that Justin needed to reach his destination after the two met
= 264 ÷ 55
= 4⁴⁴₅₅
= 4⁴₅ h

Answer(s): (a) 66 km/h; (b) 4⁴₅ h