The perimeter of the rectangle is 42 cm. Find its sides if one of them is 2 times larger than the other.

Given:

Perimeter (P) – 42 cm,

1 side (a) – x cm,

2 side (b) – 2 times more.

Find: sides a and b -? cm.

By the statement of the problem, only the perimeter is known. Suppose one side (s) x centimeters. The second side (b) is twice the size of the first, which means 2 * x.

The perimeter is found by the formula:

P = 2 * (a + b). Let’s substitute the values into the formula:

42 = 2 * (x + 2 * x). Let’s divide both sides of the equality in two:

21 = x + 2 * x.

21 = 3 * x. Let’s divide both parts into three:

7 = x,

x = 7 (cm).

Let’s calculate the second side:

2 * x = 2 * 7 = 14 (cm).

Answer: one side is 7 cm, the other is 14 cm.