Surface area The surface area of a solid is found by adding the areas of all its faces. To calculate the surface area you may first sketch the net of the shape.

Example 1 5m 9m Find the surface area of the following Base Front Right Left Top Back 5m 4m 5m 4m 9m Left/right = 2 × 4 × 5 = 40 9m 4m Base/top Base/top = 2 × 9 × 4 = 72 Back/front = 2 × 5 × 9 = 90 Back/front SA = 40 + 72 + 90 = 202m2

Example 2 Find the surface area of the following 7m 5m 12m 7m 12m 5m Back Base Front x m x2 = 52 + 122 x2 = 169 x = 13 Front = 13 × 7 = 91 Back = 5 × 7 = 35 Sides = 2 × ½ × 12 × 5 = 60 Base = 12 × 7 = 84 SA = 35 + 84 + 91 + 60 = 270m2

Example 3 12m 5m Find the surface area of the following 5 m 12 m C m What is the length of the rectangle? The same as the circumference of the circle! Rect = LB = 2πr × h = 2 × π × 5 × 12 = 377·0 Circles = 2 × πr2 = 2 × π × 52 = 157·1 OR SA = 2πrh + 2πr2 = 2×π×5×12+2×π×52 = 377·0 SA = 377·0 + 157·1 = 534·1 m2

Example 4 12 m 7 m 11 m 10 m Find the surface area of the following Base = LB = 7 × 12 = 84 Front/back = 2 × ½ × bh = 2 × ½ × 7 × 11 = 77 Sides = 2 × ½ × bh = 2 × ½ × 12 × 10 = 120 SA = 84 + 120 + 77 = 281 m2

Today’s work Exercise 6d page 203 Q1f, Q2e, 3a, 5a, 7bc, 8aeh, 9adef, 10ad, 12