<PRE><B>Question 33061</B>
The ladder leans against the wall and makes it a right-angled triangle.
The  wall and the ground are at right-angle (90 degrees)and the ladder is the
hypotunes  of the triangle.

There is a formula to find the side of the triangle(either the base or the height).
Let H be the height(unknown here) ,B be the base(18ft) and  L be the hypotunes(24 ft),
therefore,
H= SQRT(L^2-B^2)

Now substitute the values .
this gives you-  H = SQRT(24^2-18^2)
                    = SQRT(576-324)
                     = SQRT(252)
                     =15.875 ft..that is the height of the wall.

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