Find the area of a rectangle if its length is 4 cm more than its width, and the half-perimeter is 18 cm.

1. Find the perimeter of the rectangle:

18 cm x 2 = 36 cm.

2. Find the length and width of the rectangle:

Let x cm – width, then (x + 4) cm – length.

And the perimeter will be 2x + 2 (x + 4) = 36;

2x + 2x + 8 = 36;

4x + 8 = 36;

4x = 36 – 8;

4x = 28;

x = 28/4;

x = 7.

7 cm is the width of the rectangle, then 11 cm is the length.

3. Find the area of the rectangle:

S = 11 x 7 = 77 cm².

Correct answer: 77 cm².