Aria unui dreotunghi este de 405 m2,iar latimea este de 15m. calculeaza aria unui patrat care are latura egala cu un sfert din perimetrul dreptunghiului.

The area would be 441 m².

We first find the length of the given rectangle.  We know area is length times width, that the area is 405 and the width is 15; this gives us:

405 = 15L

Divide both sides by 15:
405/15 = 15L/15
27 = L

Calculate the perimeter of the rectangle:
P = 2L + 2w = 2(27) + 2(15) = 84 m

The side of the square is 1/4 the perimeter of the rectangle we just found:
1/4(84) = 21 m

The area of a square is equal to its side length squared:
A = s² = 21² = 441 m²