Question

keeping mass same of velocity of object is reduced of its limited velocity find the ratio of changed kinetic energy to the original kinetic energy

Answer 1

Since mass is constant.
The ratio will be equal to
(new vel.)^2/ (old vel.)^2

Answer 2

K.E=1/2 mv^2
since mass is const.
ratio=  changed K.E/ original K.E
        =(1/2 mv^2changed)/(1/2 mv^2original)
         =(v^2changed)/(v^2original)