Answer
The volume of the sphere decreases by a fraction of $7.69\times 10^{-4}$
The radius decreases by a fraction of $2.56\times 10^{-4}$
Work Step by Step
We can find the fraction that the volume changes:
$\frac{\Delta V}{V_0} = -\frac{1}{B}~\Delta P$
$\frac{\Delta V}{V_0} = -\frac{1}{130\times 10^9~Pa}~(100\times 10^6~Pa)$
$\frac{\Delta V}{V_0} = -7.69\times 10^{-4}$
The volume of the sphere decreases by a fraction of $7.69\times 10^{-4}$
We can find the fraction that the radius changes:
$\frac{\Delta r}{r_0} \approx \frac{-7.69\times 10^{-4}}{3} = -2.56\times 10^{-3}$
The radius decreases by a fraction of $2.56\times 10^{-4}$
