If mass of earth decreases by $25 \%$ and its radius increases by $50 \%$, then acceleration due to gravity at its surface decreases by nearly ……… $\%$

The acceleration due to gravity at height $h$ above the earth if $h \ll R$ (radius of earth) is given by

If the value of $‘g’$ acceleration due to gravity, at earth surface is $10\,m/{s^2}$, its value in $m/{s^2}$ at the centre of the earth, which is assumed to be a sphere of radius ‘R’ metre and uniform mass density is

A simple pendulum doing small oscillations at a place $\mathrm{R}$ height above earth surface has time period of $T_1=4 \mathrm{~s}$. $T_2$ would be it's time period if it is brought to a point which is at a height $2 R$ from earth surface. Choose the correct relation $[R=$ radius of Earth]:

At what altitude in metre will the acceleration due to gravity be $25\%$ of that at the earth's surface (Radius of earth $= R\, metre$)