Question

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.

Answer 1

Given :

The length of ladder that is  propped against a building = h = 21 feet

The bottom of the ladder was placed away from the base of the building= b = 4 feet

To Find :

The height of building does the ladder reach

Solution :

Let the height of building does the ladder reach = p feet

∵  From figure , This will make a right angle triangle

By Pythgoras theorem

 Hypotenuse² = Perpendicular² + Base²

i.e  h² = p² + b²

Or, ( 21 feet )²  = p² + ( 4 feet )²

Or, p²  = 441 - 16

Or, p² = 425

∴  p = $\sqrt{425}$

i.e height = p = 20.6 feet

Hence , The height of building does the ladder reach is 20.6 feet  Answer