All sides of the rectangle were enlarged by 10%. By what percentage has its area increased?

All sides of the rectangle were enlarged by 10%.

Let’s determine by what percentage its area has increased.

Let x = the original first side of the rectangle and y the original second side of the rectangle.

The initial area of the rectangle is: S = x * y.

Then, after the sides have increased by 10%, then we get the new sides of the rectangle.

x * (1 + 0.1) = 1.1 * x;

y * (1 + 0.1) = 1.1 * y.

The area of the rectangle after the change is: S = 1.1 * x * 1.1 * y = 1.21 * x * y;

1.21 * x * y / (x * y) = 1.21.

This means that the area will increase by 21 percent.