Answer
The radius of the sphere is $1.3164 cm$
Work Step by Step
We are told the mass of the sphere is 25.8 grams and the density of the sphere is 2.7 g/cm^3. Using the formula for density; $Density =\frac{Mass}{Volume}$, we can solve for the volume of the cube; $Volume =\frac{Mass}{Desnity} = \frac{25.8 g}{2.7 g/cm^3} = 9.555555556 cm^{3}$. Now to find the radius of the sphere we can simply rearrange the formula for the volume of the sphere; $V = \frac{4}{3}πr^{3}$ so $r = \frac{3V}{4π}^{\frac{1}{3}}$
$r = \frac{3\times9.555555556 cm^{3}}{4π}^{\frac{1}{3}} = 1.3164 cm$