A 15 m long ladder reached a window 12 m high from the ground on placing it against a wall at a distance a Find the distance of the foot of the ladder from the wall

Let AC be the ladder and A be the window.
Given: AC = 15 m, AB = 12 m, CB = a m
In right angled triangle ACB,
(Hypotenuse)² = (Base)² + (Perpendicular)² [By Pythagoras theorem]
⇒ (AC)² = (CB)² + (AB)²
⇒ (15)² = (a)² + (12)²
⇒ 225 = a² + 144
⇒ a² = 225 – 144 = 81
⇒ a √81 = 9 cm

Thus, the distance of the foot of the ladder from the wall is 9 m.

Class 7 Maths Chapter 6 Exercise 6.5

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