A ladder 15 m long reaches a window which is 9 m above the ground on one side of street. Keeping its foot at the same point, the ladder is turned to the other side of the street to reach a window 12 m high. What is the width of the street:

Draw a figure as per given question,
In a Right triangle ADC, Use the (Pythagoras Theorem)
AC = ?DC² - AD²
? AC = ? 15² - 9 ²
? AC = ? 225 - 81
? AC = ? 144
? AC = 12 cm
In a Right triangle BCE, Use the formula
CB = ? CD² - BE²
? CB = ?15 ² - 12²
? CB = ?225 - 144
? CB = ? 81
? CB = 9 m

? Width of the street (AC + BC) = AB = 12 + 9 = 21 m.