The volume of a sphere `= 4pi r^(3)//3` where r is the radius of the sphere
`:.` Volume of the nucleus `= 4pi r^(3)//3 = 4pi (10^(-13))^(3)//3 cm^(3)`
Similarly, Volume of the atom `= 4pi r^(3)//3 = 4pi (10^(-8))^(3)//3 cm^(3)`
`:.` Fraction of the volume of atom occupied by the nucleus `= (4pi (10^(-13))^(3)//3 cm^(3))/(4pi (10^(-8))^(3)//3) cm^(3) = 10^(-15)`