The length of each side of the square was increased by 20%. By what percentage has the area of the square increased?

Let x be the side of the square initially,

then the area of the square is S = x ^ 2.

The side of the square after enlarging is (x + 0.2 * x) = 1.2 * x.

That is, 1.2 * x * 1.2 * x = 1.44 * x ^ 2

Therefore, 1.44-1 = 0.44 * 100% = 44%.

This means that the area of the square after increasing the side will increase by 44%.

Answer: 44%.

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