To get the minimum number of cylinders, the volume of each of the cylinder must be HCF of
405,783, and 351
⇒HCF(405,783,351)=27 Therefore, number of cylinders of iron
=‌=15 and, number of cylinders of aluminum
=‌=29 and, number of cylinders of copper
=‌=13 Hence, the total number of a cylinders
=15+29+13=57 Also, volume of each cylinder
=27cc ⇒πr2h=27 ⇒π×32×h=27 ⇒h=‌ And total surface area of each cylinder
=2πr(r+h) =2π×3(3+‌)=18(π+1) Hence, total surface area of 57 cylinders
=57×18(π+1) =1026(π+1)