WAEC Mathematics 2015 Paper

Concept:The angle of elevation forms a right triangle with the height and distance. Use the sine ratio.Explanation:Let the aircraft be point $A$ and the point on ground be $K$. The height of the aircraft is the side opposite to the angle: $800$ m. The distance from $K$ to the aircraft is the hypotenuse $KA$. So, $\sin 30^\circ = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{800}{KA}$. We know $\sin 30^\circ = 0.5$. Therefore, $0.5 = \frac{800}{KA}$. This gives $KA = \frac{800}{0.5} = 1600$ m. Answer:The aircraft is $1600.00$ m from K. Correct option: D. $1{,}600.00$ m.