Question

Circumference of the base of a cylinder open at the top is 132cm. The sum of the radius and slant height of the cylinder is 41cm. Find the cost of polishing the outer surface of cylinder at the rate of ₹400 per m^{​​​​​​2.}

Answer 1

Slant height is considered as height of the cylinder.

Here given Circumference of the base of a cylinder open at the top is 132cm.
2πr=132
r=132/2π=21.
Also given that
The sum of the radius and height of the cylinder is 41cm.
r+h=41
h=41-r=41-21=20.
Given that top of the cylinder is open.So that total area is
=πr(r+2h)
​​​​​​=21π(21+40)
=4026cm^2=0.4026m^2.
The cost of polishing the outer surface of cylinder at the rate of ₹400 per m​​​​​​2 is
0.4026×400=161.04 ₹