Express as a percentage the change in area of a rectangle if its length increases by 30% and its width decreases by 30%.

Suppose the initial length of the rectangle is a.

In this case, we write the width as in.

The area of the rectangle will be equal to: a * b.

after its length increases by 30%, it will be: a + 30% = 1.3 * a.

The new width will be: in – 30% = 0.7 * in.

This means the area of the new rectangle:

1.3 * a * 0.7 * b = 0.91 * a * b.

From this it follows that the area will change to:

a * b – 0.91 * a * b = 0.09.

When converted to interest, it will be:

0.09 * 100% = 9%.

Answer: The area will decrease by 9% from the initial one.