Question 186779
Ladder makes a right triangle with the wall and ground. The hypotenuse = length of the ladder = 10 ft

Let the height be h
By Pythagorean theorem 

10^2 = 3^2 + h^2

h^2  = 10^2 - 3^2 = 100 - 9 = 91
h = sqrt( 91) = 9.54 ft