What is the total surface area of a cone which has a radius of 21 cm and a height of 28 cm? (Take $$\pi = \frac{22}{7}$$)
r = radius of cone = 21 cm
h = height of cone = 28 cm
total surface area of a cone =Â $$\pi\ \times\ r\times\left(r+\sqrt{\ r^2+h^2}\right)$$
=Â $$\frac{22}{7}\times\ 21\times\left(21+\sqrt{\ \left(21\right)^2+\left(28\right)^2}\right)$$
= $$22\times3\times\left(21+\sqrt{\ 441+784}\right)$$
= $$66\times\left(21+\sqrt{1225\ }\right)$$
= $$66\times\left(21+35\right)$$
= $$66\times56$$
=Â 3696Â $$cm^2$$
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