A is twice as fast as B and B is thrice as fast as C is. The journey covered by C in 1\frac{1}{2} hours will be covered by A in :
[A]15 minutes
[B]20 minutes
[C]30 minutes
[D]1 hour

15 minutes
Let speed of B = x km/hr
Speed of A = 2x km/hr
Speed of C = \frac{x}{3}\ km/hr
\therefore \frac{Speed\ of\ A}{Speed\ of\ C} = \frac{2x}{\frac{x}{3}} = 6
∴ Required Time = \frac{1}{6}\ of \frac{3}{2}\ hours = \frac{1}{4}\ hours = 15\ minutes
Hence option [A] is correct answer.