In a 1 km race, X beats Y by 20 seconds and Y beats Z by 10 seconds. If X beats Z by 240 m. The time taken by X to run 1 km is:

95 sec

    X   :       Y        :    Z

    x   :  (x + 20)   : (x + 30)

Same is the ratio of distance 

Difference between X and Z = 240 is covered 30 seconds

Speed of Z = 8 m/s

Time taken to cover 1km  = \(\frac{1000}{8}\) = 125 seconds 

Time taken by X = 125 - 30 = 95 seconds