Andrew is standing next to s building whose shadow is 15 ft long. If Andrew is 6 ft tall and is casting a shadow 2.5 ft long, how high is the building?

The building is 36 feet high.

proportionality.

a / b = c / d

a = height of andrew

b = andrew's shadow

c = height of the building

d = building's shadow

where: cross products are equal.

6 / 2.5 = x / 15

6 (15) = 2.5x

90 = 2.5x

90/2.5 = 2.5x / 2,5

36 = x height of the building in feet