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:

Let the height of the building x metres.

Less lengthy shadow, Less in the height (Direct Proportion)

 40.25 : 28.75 :: 17.5 : x        40.25 x x = 28.75 x 17.5

 x = 12.5