Question

A 13 foot ladder is placed

Answer 1

Answer: 12 feet up

Step-by-step explanation:

This problem models a right triangle, in which the ladder is the hypotenuse and the distance away from the wall is one of the legs.  Thus, you may use the Pythagorean Theorem (a^2 + b^2 = c^2)

$a^2+b^2=c^2\\5^2+b^2=13^2\\25+b^2=169\\b^2=144\\b=12$

N.B. There are some very useful sets of numbers that can help you with this unit.

They are called Pythagorean triplets, and they are the sets of whole numbers that make right triangles.  The important ones are 3, 4, 5, and 5, 12, 13 (And their multiples, like 6, 8, 10(3,4,5 *2))

Hope it helps :) and let me know if you want me to elaborate further.