CAT 2019 Shift 2 Paper

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 =‌

405

27

=15
and, number of cylinders of aluminum =‌

783

27

=29
and, number of cylinders of copper =‌

351

27

=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=‌

3

π

And total surface area of each cylinder =2πr(r+h)
=2π×3(3+‌

3

π

)=18(π+1)
Hence, total surface area of 57 cylinders =57×18(π+1)
=1026(π+1)