If the diameter of an atom is 1 × 10-8 cm, what is the approximate diameter of its nucleus

Here we have to find the diameter of nucleus as the diameter of atom is given.
Diameter of atom is 1 x 10⁻⁸ cm
Radius of atom = diameter/2
so, radius of atom = 1 x 10⁻⁸ cm/2 = 5 x 10⁻⁹ cm
To find diameter of nucleus, first we have to find the radius of nucleus by using this formula,
R = rA⁽¹/³⁾     where R = radius of nucleus, r = radius of atom and A is a nucleon number, which is different for every atom
so, R=(5x10⁻⁹)A⁽¹/³⁾  
here atom is not mentioned, so we don't know the value of A
and Dimeter (D) = 2R, R = D/2
 D/2 = (5x10⁻⁹)A⁽¹/³⁾
Diameter of nucleus (D) = 2((5x10⁻⁹)A⁽¹/³⁾)