The radii of the top and bottom of a12 cm deep tub are 20cm and 10 cm. Find the cost of tin sheet used for making the tub at the rate of rs 1.20 per cm square.

R=20 cm
r=10 cm
h=12 cm
l=sq. root[H²+(R-r)^​2]
=sq root[144+100]
=2*7.9
=15.8 cm


tin sheet used =csa of frustum + are of base
​                       pi  l {R+r}   +pi r²
                    3.14  *15.8{30}  +3.14 *100
                  1488[approx]+314
                  =1812 cm{approx}

cost=1.20*1812=rs.2175 {approx}