City R and City S are 600 km apart. At 1.18 p.m., Vaidev is travelling at a uniform speed left City R for City S while Riordan set off from City S to City R along the same road at a uniform speed, which was 8 km/h slower than that of Vaidev. The two met at 4.18 p.m.

1. Find the speed of Vaidev.
2. If Riordan 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 Vaidev and Riordan to travel from 1.18 p.m. to 4.18 p.m. = 3 h

Average speed of Vaidev and Riordan
= 600 ÷ 3
= 200 km/h

Vaidev's speed
= (200 + 8) ÷ 2
= 208 ÷ 2 
= 104 km/h

(b)
Riordan's speed
= 104 - 8
= 96 km/h

Distance that Riordan travelled in 3 h
= 3 x 96
= 288 km

Remaining distance that Riordan needed to travel
= 600 - 288
= 312 km

Time that Riordan needed to reach his destination after the two met
= 312 ÷ 96
= 3²⁴₉₆
= 3¹₄ h

Answer(s): (a) 104 km/h; (b) 3¹₄ h