Motor-cyclist P started his journey at a speed of 30 km/hr. After 30 minutes, motor cyclist Q started from the same place but with a speed of 40 km/hr. How much time will Q take to overtake P?
[A]1\ hours
[B]\frac{3}{8}\ hours
[C]\frac{3}{2}\ hours
[D]2\ hours

\mathbf{\frac{3}{2}\ hours}
Distance covered by motor cyclist P in 30 minutes.
= 30\times \frac{1}{2} = 15\ km
Relative Speed = 40 – 30 = 10 km/hr
∴ Required Speed = Time taken to cover is km at 10 km/hr
= \frac{15}{10} = \frac{3}{2}\ hours
Hence option [C] is correct answer.