WAEC Mathematics 2018 Paper

Concept:The unshaded area is obtained by subtracting the shaded area from the total area of the rectangle.Explanation:The rectangle $WXYZ$ measures $8\text{ cm}$ by $6\text{ cm}$, so the total area is:$$8 \times 6 = 48\text{ cm}^2$$Since $P$, $Q$, $R$ and $S$ are midpoints, the shaded region is the rhombus $PQRS$.The diagonals of this rhombus are equal to the length and width of the rectangle, that is $8\text{ cm}$ and $6\text{ cm}$.Thus, area of the rhombus is:$$\frac{1}{2} \times 8 \times 6 = 24\text{ cm}^2$$Therefore, the area of the unshaded part is:$$48 - 24 = 24\text{ cm}^2$$Answer:$24\text{ cm}^2$ (Option B).