The width of the rectangle is 5 cm and its perimeter is 2 dm 8 cm, find the area of the rectangle.

answer: the area of the rectangle is 45 cm2

decision:

according to the conditions of the problem, the perimeter of the rectangle is 2 dm 8 cm. Let’s translate this value into centimeters. we get 2 dm 8 cm = 28 cm.

the perimeter of the rectangle is twice the sum of the two sides (length and width).

the width of the rectangle is 5 cm. Find the length of the rectangle.

P = 2 * (a + b), b = 1/2 * P – a.

we get that the length of the rectangle is 9 cm (b = 1/2 * 28 – 5)

the area of a rectangle is equal to the product of its two sides, i.e. S = a * b. we get that the area of the rectangle is 45 cm2 (S = 5 * 9)