Instruction

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Prjamougolnosti: find the perimeter of a rectangle if you know that the area is equal to 18, and the length of a rectangle is 2 times the width.Solution: write the formula for area of a rectangle S = a*b. The statement b = 2*a, hence 18 = a*2*a, a = √9 = 3. It is obvious that b = 6. According to the formula the perimeter is equal to the sum of all the sides of the rectangle P = 2*a + 2*b = 2*3 + 2*6 = 6 + 12 = 18. In this problem the perimeter is matched by value with the area of the figure.

2

Quadratscha: find the perimeter of a square if its area is 9.Solution: by formula the area of a square S = a^2, hence find the length of side a = 3. The perimeter is equal to the sum of the lengths of all sides hence P = 4*a = 4*3 = 12.

3

Treugolnika: given an arbitrary triangle ABC, the square of which is equal to 14. Find the perimeter of a triangle, if drawn from the vertex B, the altitude divides the base of the triangle into segments of length 3 and 4, see the Solution: by formula the area of a triangle is half the work of the Foundation to the height, i.e., S = ½*AC*BE. The perimeter is equal to the sum of the lengths of all sides. The length of the side AC find the folding of the lengths AE and EC, AC = 3 + 4 = 7. Find the height of the triangle BE = S*2/AC = 14*2/7 = 4.Consider the right triangle ABE. Knowing the legs AE and BE, we can find the hypotenuse by the formula of Pythagoras, AB^2 = AE^2 + BE^2, AB = √(3^2 + 4^2) = √25 = 5.Consider the right triangle BEC. By the formula of Pythagoras BC^2 = BE^2 + EC^2, BC = √(4^2 + 4^2) = 4*√2.Now known the lengths of all sides of the triangle. Find the perimeter of their sum P = AB + BC + AC = 5 + 4*√2 + 7 = 12 + 4*√2 = 4*(3+√2).

4

Ukrainetoday: it is known that the area of the circle is 16*PI, find its perimeter.Solution: write the formula for area of a circle S = π*r^2. Find the radius of the circle r = √(S/π) = √16 = 4. According to the formula of the perimeter P = 2*π*r = 2*π*4 = 8*π. If we assume that π = 3.14, P = 8*3.14 = 25.12.

# Advice 2: How to find the area and perimeter of a square

A square is a geometrical figure consisting of four sides of equal length and four right angles, each of which is equal to 90°. Determine the area or

**of a quadrilateral, with anyone, is required not only when solving problems in geometry and in everyday life. These skills can be useful, for example, during repairs when calculating the right amount of materials - floor coverings, walls or ceiling, as well as a breakdown of lawns and garden beds etc.****perimeter**Instruction

1

To find the area

*of a square*multiply the length value by the value of width. As the square length and width are the same, then the value enough to square. Thus, the area of a square equals length of its side squared. A unit of area can be square millimeters, centimeters, decimeters, meters, kilometers.To determine the area of a square, you can use formulas = aa, where S is the area of a square and the side of the square.2

Example No. 1. The room is square-shaped. How much plastic (in square metres) will be required in order to completely cover the floor, if the length of one side of the room is 5 meters.Write down the formula: S = aa. Substitute it specified in the condition data.Since a = 5 m, hence the area will be Ravna (room) = 5x5= 25 sq m, so and S (laminate) = 25 sq. m.

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The perimeter is the total length of the border. Squared perimeter is the length of all four, with the same sides. That is, the perimeter of the square is the sum of all its four sides. To calculate the perimeter of a square, it is sufficient to know the length of one side. Perimeter is measured in millimeters, centimeters, decimeters, meters, kilometers.To define a perimeter formula:P = a + a + a + a Ilir = 4a, gder perimeter,and side length.

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Example No. 2. For finishing works of the premises in the form of a square required ceiling moldings. Calculate the total length (perimeter) skirting, if the value of one side of the room is 6 meters. Write down the formula P = 4a.Substitute it specified in the condition data:P (room) = 4 x 6 = 24 meters.Consequently, the length of the ceiling moldings will also be equal to 24 meters.