The side length of the square was increased by 20%. How much percentage has its area increased?

Before increasing the side, the area of the square is:

S1 = a * a;

After enlargement:

S2 = 1.2 * a * 1.2 * a;

Let’s make the proportion:

a * a = 100%;

1.2 * a * 1.2 * a = x%;

Let us express x from here:

x = 1.2 * a * 1.2 * a * 100% / a * a = 1.2 * 1.2 * 100% = 1.44 * 100% = 144%;

Then the area increased by:

144% – 100% = 44%;

Answer: 44%.