How does the area of a rectangle change if a) its length and width are reduced by 10%

How does the area of a rectangle change if a) its length and width are reduced by 10%; b) increase its length by 30%, and reduce its width by 30%

The area of a rectangle is equal to the product of its adjacent sides of length a and width c

S = ac.

a) If the length and width of the rectangle decrease by 10%, then they will be 0.9a and 0.9c, which means the area of the rectangle will be equal to

0.9a * 0.9c = 0.81 ac = 0.81 S.

The area of the rectangle will decrease by 100% – 81% = 19%.

b) If the length of the rectangle is increased by 30%, and the width is reduced by 30%, then they will be equal to 1.3a and 0.7c, which means the area will be

1.3a * 0.7c = 0.91 ac = 0.91 S.

The area will decrease by 100% – 91% = 9%.