If kinetic energy of a body is increased by 300% then percentage change in momentum will be

Momentum and kinetic energy: $P = \sqrt{2mE}$
Increase of 300 percent means $E_2 = E_1 + 3E_1 = 4E_1$.
$P_2 = \sqrt{2m(4E_1)} = 2\sqrt{2mE_1} = 2P_1$
Percentage change $= \dfrac{P_2 - P_1}{P_1} \times 100 = \dfrac{2P_1 - P_1}{P_1} \times 100 = 100$ percent
So the momentum increases by 100%.