Let the mass of electron is halved, mass of proton is doubled and mass of neutron is made three fourth of original mass. Mass number of O-16

Mass of electron is negligible.It is not considered while calculating mass number ;

Actual mass number = 8 p + 8 n = 16 ;

 $$\begin{gathered} \mathrm{New} \mathrm{mass} \mathrm{number} : \\ \left(8\times 2\right) \mathrm{p}+\left(\frac{3}{4}\times 8\right)\mathrm{n}=22 \\ 6 \mathrm{units} \mathrm{increase} \mathrm{for} 16 \\ \% \mathrm{increase} =100\times \frac{6}{16}=37.5\% \end{gathered}$$