If the area of a square of side 40 m is equal to the area of a rectangle of width 20 m, then the length of the rectangle is _____ m.

It is given that, the side of the square = 40 m

Therefore, the area of the square = side × side = 40 m × 40 m = 1600 m²

It is also given that, the width of the rectangle = 20 m

It is known that the area of a rectangle = length × width

Given, the area of the rectangle = area of the square

∴ The length of the rectangle × 20 m = 1600 m²

⇒ The length of the rectangle = $\frac{1600}{20}=80 \mathrm{m}$

Thus, the required length of the rectangle is 80 m.