what is surface area

The surface area of sphere is 4 * `Pi` * r2 square units.Let us see sample problems for the surface area of sphere,Example 1:Find the surface area of the sphere which is of radius equal to 7 cm.solution:Given the radius of the sphere: (r) = 7 cm.we need to find surface area of the sphere.we know surface area of sphere is given by 4 * `Pi` * r2 cubic units.substitute the radius, r = 7 cm in the formula,volume of the sphere = 4 * 3.14 * 72 = 4 * 3.14 * 7 * 7volume of the sphere = 615.44 cm2Example 2:Find radius of sphere which is of surface area equal to 615.44 cm2.solution:Given the surface area of the sphere: 615.44 cm2To find radius of sphere.we know volume of sphere is given by 4*`Pi` * r2 cubic units.equate the given volume of sphere with the formula,volume of the sphere = 4 * 3.14 * r2 615.44 cm2 = 4 * 3.14 * r2 r2 = 615.44 * `(1/4)` * `(1/(3.14)) ` cm2 r2 = 49 r = 7 cm.