City Q and City R are 426 km apart. At 2.50 p.m., Xavier is travelling at a uniform speed left City Q for City R while Mark set off from City R to City Q along the same road at a uniform speed, which was 10 km/h slower than that of Xavier. The two met at 5.50 p.m.

1. Find the speed of Xavier.
2. If Mark 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 Xavier and Mark to travel from 2.50 p.m. to 5.50 p.m. = 3 h

Average speed of Xavier and Mark
= 426 ÷ 3
= 142 km/h

Xavier's speed
= (142 + 10) ÷ 2
= 152 ÷ 2 
= 76 km/h

(b)
Mark's speed
= 76 - 10
= 66 km/h

Distance that Mark travelled in 3 h
= 3 x 66
= 198 km

Remaining distance that Mark needed to travel
= 426 - 198
= 228 km

Time that Mark needed to reach his destination after the two met
= 228 ÷ 66
= 3³⁰₆₆
= 3⁵₁₁ h

Answer(s): (a) 76 km/h; (b) 3⁵₁₁ h