A 15 m long ladder reached a window 12 m high form the ground on placing it against a wall at a distance a. Find the distance of the foot of the ladder from the wall.
It is given in the question that,
Length of ladder = 15 m
Height of ladder = 12 m
We have to find the distance of the foot of the ladder from the wall
Let the distance be a
According to Pythagoras theorem,
In a right angled triangle:
(Hypotenuse)2 = (Perpendicular)2 + (Base)2
By applying Pythagoras theorem in the given question, we get:
(15)2 = (12)2 + (a)2
225 = 144 + (a)2
(a)2 = 225 - 144
(a)2 = 81
Hence,
a = 
a = 9 m
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