A flagstaff 17.5 m high casts a shadow of length 40.25 m. The height of the building, which casts a shadow of length 28.75 m under similar conditions will be
(a)10 m
(b)12.5 m
(c)17.5 m
(d)21.25 m
Answer
Answer (as printed): B
Explanation
Let the height of the building be $x$ metres. Less lengthy shadow, Less is the height (Direct Proportion) $$\begin{aligned} & \therefore \quad 40.25: 28.75:: 17.5: x \\ & \Leftrightarrow \quad 40.25 \times x=28.75 \times 17.5 \\ & \Leftrightarrow x=\frac{(28.75 \times 17.5)}{40.25} \Leftrightarrow x=12.5 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.