A tree 4.8 m high casts a shadow 9 m long. At the same time, what is the length of the shadow of a building 43.2 m high?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 81 m
At the same time of day the sun's rays fall at the same angle, so height and shadow are in the same ratio for every object: they are in direct proportion.
\(\displaystyle \frac{4.8}{9}=\frac{43.2}{x}\)
\(\displaystyle x=\frac{43.2\times9}{4.8}\)
\(43.2\div4.8=9\), so \(x=9\times9=81\)
The shadow of the building is 81 m long.