Question

If a 36-foot tree casts a 28-foot shadow at the same time near by building casts a 70-foot shadow, how tall is the building?

Answer 1

The building is 78 feet tall.

Answer 2

actual length / shadow ratio is equal
Let the height of the building be x, then
36/28 = x/70
x = (36 x 70)/28 = 2,520/28 = 90.

Therefore, the height of the building is 90 feet.