The increase in square feet when the garden is enlarged is 400 square feet.
The first step is to determine the perimeter of the fence:
Perimeter = 2( length + width)
2 (60 + 20)
= 160 feet
When the shape of the garden is changed to a square, the perimeter of the square and the rectangle has to be the same.
Length of side of the square = 160 / 4 = 40 feet
Area of the square = 40 x 40 = 1600 square feet
Area of the garden = 60 x 20 - 1200 square feet
Difference = 1600 - 1200 = 400 square feet
To learn more about how to calculate the area of a rectangle, please check: https://brainly.com/question/16595449
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