Derive the formula for the curved surface area and total surface area of the frustum of a cone, given to you in Section 13.5, using the symbols as explained.
Let h be the height, l the slant height and r1 and r2 the radii of the circular bases of the frustum ABB’ A’ shown in Fig. such that r1 > r2. Now,Height of the cone VA‘B’ Slant height of the cone VA‘B’ Let S denote the curved surface area of the frustum of cone. Then,S = Lateral (curved) surface area of cone VAB - Curved surface area of cone VA‘B’ [Using (A) and (C)] Curved surface area of the frustum = π (r1 + r2) I + πr12 + πr22 > Solution Volume of each cube = 125 cm3 So, edge of each cube = 5 cm For new cuboid formed, l = 5+5 = 10 cm b = 5 cm h = 5 cm Therefore, surface area of the resulting cuboid = 2 (lb + bh + lh) = 2 (10 × 5 + 5 × 5 + 10 × 5) cm2 = 250cm2 Mathematics Secondary School Mathematics X Standard X Suggest Corrections 12 |