Let k1 be the initial kinetic energy,k2 be the final kinetic energy.
let p1 be intial momentum & p2 be final momentum.
From question we have,
k2=k1+100%k1
k2=k1+k1=2k1
1\2(mV2)2=2(1\2mV12)
V2=√2V1
on mutiplying by mass m,
mV2=√2mV1
p2=√2p1. now,
Δp=p2-p1
=>p1(√2-1)
%age of change in momentum=100(Δp\p1)
= 100(√2 - 1) %
=(1.414-1)100
=41.4%