Question

Question 28

If R is the radius of the base of the hat, then the total outer surface area of the hat is

a) $\pi r(2h+R)$
b) $2\pi r(h+R)$
c) $2\pi rh+\pi R^2$
d) None of these

Answer 1

Given, a cylindrical hat with base radius R and r is the radius of the top surface.
Now, total surface area of hat = Curved surface area + Top surface area + Base surface area
$=2\pi rh+\pi r^2+\pi (R^2-r^2)=2\pi rh+\pi r^2+\pi R^2-\pi r^2=2\pi rh+\pi R^2$