The sum of the adjacent sides of the rectangle is 20cm. Find its area if the length is 4cm more than the width.

If it is known that one of the sides is 4 cm larger than the other, then denoting the smaller side for x cm, the other will be equal to (x + 4) cm.

Because by the condition of the problem, the sum of adjacent sides gives 20 cm, we obtain the following equation:

1) x + (x + 4) = 20,

2x + 4 = 20,

2x = 16,

x = 16/2,

x = 8.

Let’s calculate what the length of the longer side is equal to:

2) 8 + 4 = 12 (cm).

Thus, having calculated the product of adjacent sides – length and width, we determine the area of the rectangle:

3) 12 * 8 = 96 (cm2).

Answer: the area of the rectangle is 96 cm2.