# If a 30 m ladder is placed against a 15 m wall such that it just reaches the top of the wall, then the elevation of the wall is equal to?

A. 45° B. 30° C. 60° D. 50° Answer: Option B
$\begin{array}{l} \mathrm{AC}=30 \text { meter } \\ \mathrm{AB}=15 \text { meter } \\ \angle \mathrm{ACB}=\theta \\ \therefore \sin \theta=\frac{A B}{A C}=\frac{15}{30}=\frac{1}{2} \\ \Rightarrow \sin \theta=\sin 30^{\circ} \\ \Rightarrow \theta=30^{\circ} \end{array}$