A ladder that is 21 feet long is propped against a building. The bottom of the ladder was placed 4 feet from the base of the building. How high up on the building does the ladder reach? Round the answer to the nearest tenth of a foot

20.62 feet

Step-by-step explanation:

The ladder propped against a building forms a right angle triangle

Height of the ladder (hypotenuse) = 21 feet

Base of the ladder from the building (adjacent) = 4 feet

Height of the building (opposite) = x feet

Hypotenuse ² = opposite ² + adjacent ²

21² = x² + 4²

21² - 4² = x²

441 - 16 = x²

425 = x²

x = √425

= 20.62 feet