If the K.E. of a body is increased by 300%, its momentum will increase by (in %)

Let initial kinetic energy, ${\mathrm{E}}_1=\mathrm{E}$

Final kinetic energy, ${\mathrm{E}}_2=\mathrm{E}+300\mathrm{\%}$ of E = 4E

As $\mathrm{P}\propto \sqrt{\mathrm{E}}\Rightarrow \frac{{\mathrm{P}}_2}{{\mathrm{P}}_1}=\sqrt{\frac{{\mathrm{E}}_2}{{\mathrm{E}}_1}}=\sqrt{\frac{4\mathrm{E}}{\mathrm{E}}}=2\Rightarrow {\mathrm{P}}_2=2{\mathrm{P}}_1$

$\Rightarrow {\mathrm{P}}_2={\mathrm{P}}_1+100\mathrm{\%}$  of  P₁

i.e. Momentum will increase by 100%.