Question 49784
If you were to sketch a diagram of this situation, you would see a picture of a right triangle whose base is the distance of the base of the ladder from the wall (10 ft.) and whose height is the distance from the top of the ladder to the floor (11 ft.). The ladder itself forms the hypotenuse of this right triangle and you are being asked to find its length.
Remember the Pythagorean theorem? In any right triangle, the sum of the squares of the lengths of the two sides is equal to the square of the length of the hypotenuse. {{{c^2 = a^2+b^2}}} where c is the length of the hypotenuse (ladder).

{{{c^2 = 10^2+11^2}}}
{{{c^2 = 100+121}}}
{{{c^2 = 221}}} Take the square root of both sides.
{{{c = 14.8660687473}}}
{{{c = 14.866}}}feet, to the nearest thousandth.