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A 35 feet long steel bar is leaning against a wall that is perpendicular to the floor. The bottom end of the steel bar is 21 feet away from the wall. If the steel bar slides down the wall by 7 feet, how far does the bottom end move away from the initial position?

(1) 7
(2) 9
(3) 6
(4) 8
(5) 5

This forms a right triangle, whose hyp = 35.

One of its sides is given to be 21. Thus, other side = 35^2 - 21^2 = sqrt (784) = 28

If the steel bar slides 7 feet down from the wall, the distance of the top portion from the bottom of the wall is 28 - 7 = 21. Now, since the hyp of the triangle, i,e the length of the steel is the same, the slide in the bottom end has to be 7 feet so as to keep the same pythagorian triplets.