A 15 foot ladder is leaning against the wall of a house. If the base of the ladder is 6 feet from the house how far up the wall does the ladder reach
Pythagorean theorem:
a² + b² = c²
a² = c² - b²
a = √ ( c² - b²)
In this case:
b = 6 ft , c = 15 ft
a = √ ( c² - b²) = √ ( 15² - 6²) =
√ ( 225 - 36 ) =√ 189 = 13.748 ft