Question

A 20 foot ladder is leaning against a 25 foot building. The bottom of the ladder is 9 feet away from the building. How high is the top of the ladder above the ground?

Answer 1

17.9 feet

Explanation:

This is a right triangle

the 20 foot ladder is the hypotenuse

The 9 foot at the bottom is one leg

The height is the remaining leg

Use the pythagorean theorem

a² + b² = c²

a² + 9² = 20²

Subtract 9² from both sides

a² = 20² - 9²

a² = 400 - 81

a² = 319

Take the square root of both sides

a = 17.860571099491752

rounded

17.9 feet

Answer 2

A ladder is the hypotenuse of the right triangle.

Missing leg is x.

Use Pythagorean:

• x² = 20² - 9²
• x² = 319
• x = √319
• x = 17.86 feet or 18 feet rounded