P and Q are 27 km away. Two trains with speed of 24 km/hr and 18 km/hr respectively start simultaneously from P and Q and travel in the same direction. They meet at a point R beyond Q. Distance QR is :

Answer: Option B

Relative speed = 24 - 18 = 6 km/hr
Time required by faster train to overtake slower train :
= $$\frac{27}{6}$$
= $$4\frac{1}{2}$$ hr
∴ Distance between Q and R :
= 18 × $$4\frac{1}{2}$$
= 81 km