How high does the ladder reach up the wall?

Regis leans a 10 foot ladder against a wall. The base of the ladder is 4 feet from the wall. How high does
the ladder reach up the wall?

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A right triangle is formed, with the ladder being the hypotenuse of the right triangle.

Pythagorean Theorem
a² + b² = c² {in a right triangle, the sum of the squares of the legs is equal to the square of the hypotenuse}
4² + b² = 10² {the base of the ladder and the height up the wall are the legs of the right triangle}
16 + b² = 100 {evaluated exponents}
b² = 84 {subtracted 16 from each side}
​b ≈ 9.2 {took the square root of each side}

The ladder reaches approximately 9.2 feet up the wall.

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