The ratio of the speed of Aman, Kamal and Manan is 2 : 3 : 4 respectively. What is the ratio of the time taken by Aman, Kamal and Manan respectively to cover the same distance?

6 : 4 : 3

The ratio of time ∝ $\frac{1}{speed}$ when distance is same 

                         Aman  :  Kamal  : Manan

Speed                  2      :      3      :     4

Time                    $\frac{1}{2}$      :      $\frac{1}{3}$      :     $\frac{1}{4}$      (the inverse of a ratio)

                           6      :     4       :     3