WAEC Mathematics 2013 Paper

Concept:The curved surface area of the cone is equal to the area of its sector when the cone is unrolled into a flat circle.Explanation:First, find the slant height $l$ of the cone using Pythagoras' theorem:$l^2 = 96^2 + 28^2$$l^2 = 9216 + 784 = 10000$$l = \sqrt{10000} = 100\ \text{cm}$The curved surface area of the cone is given by $\pi r l$:$\text{Area} = \frac{22}{7} \times 28 \times 100$$\text{Area} = 8800\ \text{cm}^2$Since this is the same as the area of the sector, the sector area is $8800\ \text{cm}^2$.Answer:The area of the sector is $8800\ \text{cm}^2$. The correct option is A.