a ladder 16m long reaches a window which is 9m above the ground on one side of the street keeping,its foot at the same point the ladder is turn to the other side of the street to reach a window 12m high .find the width of th street.

In Δ ABC, apply Pythagoras theorem 

AC2 = AB2 + BC2

⇒ (16)2 = (9)2 + (BC)2

⇒ 256 = 81 + (BC)2

⇒  (BC)2 = 175m

⇒ BC = m

Now In Δ CED, apply Pythagoras theorem 

CE2 = ED2 + CD2

⇒ (16)2 = (12)2 + CD2

⇒ 256 = 144 + CD2

⇒ CD = m

∴ Width of the street = BC + CD =   + m =

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 Using the Pythagoras theorem, we will find the distance between the foot of the ladder and the wall. When the ladder is turned  we have to find the distance between the foot of the ladder and the wall, then add the two lengths to find the width of the street. 

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