Answer :

Sarah wants to buy a carpet for a square room with an area of 400sq ft.

the length of the room is 20ft.

Area is a quantity that describes the extent of an area on a plane or curved surface. The area of ​​a planar region or planar region refers to the area of ​​a shape or planar layer, and surface area refers to the area of ​​an open surface or boundary of a three-dimensional object. Wikipedia

The area is the area occupied by a two-dimensional figure. That is, it is a quantity that measures the number of unit squares that cover the surface of a closed figure. The standard unit of area is the square unit, commonly expressed in square inches, square feet, and so on.

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