Question

at a particular time of a day a 7 m high flag staff casts a shadow which is 8.2 m long what is the building which casts a shadow 20.5 m in length at the same moment

Answer 1

A flag is perpendicular to its shadow =>
$\frac{7}{8.2} = \frac{x}{20.5}$
=> x = 17.5 m