A 5ft ladder is leaning against a 4 ft wall. how far must the bottom of the ladder be from the wall so that the top of the ladder rests on the top of the wall?

The ladder leaning against the wall forms a right angled triangle with the gound and the wall. So we can use the formula:

a² + b² = c²

The ladder is the hypotenuse c²

The vertical leg is b²

The base or horizontal leg is a²

We need to find the length of the base a², so:

a² = c² - b²

a² = 5² - 4²

a² = 25 - 16

a² = 9

a = √9

a = 3

Therefore the bottom of the ladder must be 3 feet from the wall.