# The area of the rectangle is 720 cm2. Find the sum of the lengths of its sides if the length of the rectangle is 80 cm.

January 31, 2021 | education

| 1) Find the width of the rectangle, knowing the length and area. Let’s write the formula for the area of a rectangle:

S = a × b,

where a is the length of the rectangle, b is the width.

Let us express the width, b from the formula:

b = S: a.

Let’s calculate:

b = 720: 80 = 9 cm.

2) The sum of the lengths of all sides of a geometric figure is the perimeter. The perimeter of a rectangle is the sum of the length and width of the rectangle multiplied by 2. Let’s write the formula:

P = (a + b) × 2,

Let’s make the calculations:

P = (80 + 9) × 2 = 89 × 2 = 178 cm.

Answer: the sum of the lengths of the sides of the rectangle (perimeter) is 186 cm.