Question

the csa of rt. circular cone is 490cm2 and radius of base is 20cm find its l and tsa

Answer 1

CONE:-

          radius = r = 20cm

             CSA = 490cm²

               πrl = 490

22/7 × 20 × l = 490

                   l = (490 × 7) ÷ 22 × 20

                ∴ l = 3430 ÷ 440

∴ l = 7.795cm (or) 7.8cm

TSA of cone = πr( l + r )

                     = 22/7 × 20 (7.8 + 20)

                     = 22/7 × 20 × 27.8

                    = 12232 ÷ 7

∴ TSA = 1747.428cm²

Answer 2

GIVEN; CSA=490 CM^2

CSA=πRL

=22/7*20*L=490

L=490*7/22*20

L=7.8 CM APPROX.

TSA=πR[L+R]

=22/7*20[7.8+20]

=1747.42 CM^2