The perimeter of the rectangle is 30 cm, one of its sides is 4 times larger than the other. Find the area of this rectangle?

To find the area, you first need to find what the sides are equal to. Let x cm be one side of the rectangle, then the second side, which is four times larger, will be 4x cm.
From the perimeter formula, side a is equal to: a = P / 2 – b. We get the equation:
x = 30: 2 – 4x
x = 15 – 4x
5x = 15
x = 15: 5
x = 3. We found one of the sides, then the second side can also be found, knowing that it is four times larger:
3 * 4 = 12 (cm).
Find the area by multiplying the length and width:
12 * 3 = 36 cm2.
Answer: the area is 36 cm2.