Find the radius (r) of an aluminum cylinder that is 2.60 cm long and has a mass of 13.1 g . for a cylinder, v=πr2l. (the density of aluminum is 2.70 g/cm^3.)

Volume of Aluminium cylinder  =  mass  ÷  density
                                                 =  13.1 g  ÷  2.70 g / cm³
                                                 =  4.85 cm³

If Volume of Cylinder =  πr²l
then            4.85 cm³ =   πr²(2.60cm)
thus    r²  =  
  ∴       r   ≈  √(0.594 cm)
               ≈ 0.771 cm