Instruction

1

If you know the radius (r) of the base cylinder, all the other dimensions are not important in the calculations. Calculate the product of the number PI rounded to the desired degree of accuracy, the squared radius is and the area of base of cylinder (S): S=π*r2. For example, if the diameter (which, as you know, twice the radius) of the cylinder is equal to 70cm, and the result of the computation is required to obtain accurate up to the second decimal place (hundredths of a centimeter), then the footprint will be 3,14*(70/2)2 = 3,14*352 = 3,14*1225 ≈ 3848,45см2.

2

If the radius and the diameter is unknown, but the height (h) and volume (V) of the cylinder, then these parameters will also be sufficient to find the area (S) of the Foundation figures, just divide the volume by the height: S=V/h. For example, if the volume is equal to 950см3 and height in 20cm cylinder will have a base area of 950/20=47,5см2.

3

If in addition the height (h) of the cylinder is known the area of its lateral surface (p), then to find the area of the base (S) take the lateral surface area in the square and divide the result by four times the product of the number PI squared height: S=p2/(4*π*h2). For example, if the lateral surface area equal 570см2, then at the height of the cylinder is 25cm and the desired accuracy of computations in one hundredth of a centimeter, it needs to have a footprint equal to 5702/(4*3,14*252) = 324900/(12,56*625) = 324900/7850 ≈ 41,39см2.

4

If besides the area of the lateral surface of the cylinder (p) are known and the area of the whole surface (P), then subtracting the second from the first, remember to divide the result in half, as the total area includes both bases of the cylinder: S=(P-P)/2. For example, if the total area of the spatial shape is 980см2, and the area of its lateral surface - 750см2, the area of each base is equal to (980-750)/2=115см2.

# Advice 2: How to find the area, if you know the diameter

Knowing only the length

**of the diameter**of the circle, you can calculate not only**square**the circle but also the square of some other geometrical figures. This follows from the fact that the diameters of the inscribed or circumscribed around the shapes of the circles coincide with the lengths of their sides or diagonals.Instruction

1

If you need to find

**the area**of a circle (S) for the length of its**diameter**(D), multiply the number PI (π) on the squared length**of the diameter**, and the result divide by four: S=2 π*D2/4. For example, if the diameter of the circle is twenty inches, then its**area**can be calculated as: 3,142 * 202 / 4 = 9,86 * 400 / 4 = 986 square centimeters.2

If you need to find

**the area**of a square (S) on the diameter described around the circumference (D), construct the length**of diameter**square, and the result is split in half: S=D2/2. For example, if the diameter of the circumscribed circle is twenty inches, then**the area**of square can be calculated as: 202 / 2 = 400 / 2 = 200 square centimeters.3

If

**the area**of a square (S) you need to find the diameter of the inscribed circle (D), it is enough to build the length**of the diameter**in square: S=D2. For example, if the diameter of the inscribed circle is twenty inches, then**the area**of square can be calculated as: 202 = 400 square centimeters.4

If you need to find

**the area**of a right triangle (S) according to the known**diameter**of the inscribed m (d) and described (D) circles around it, then build the length**of the diameter of**the inscribed circle in the square and divide by four, and to the result add half the product of the lengths of the diameters of the inscribed and circumscribed circles: S=d2/4 + D*D/2. For example, if the diameter of the circumscribed circle is twenty inches, and inscribed to ten centimeters, then**the area**of the triangle can be calculated as: 102 / 4 + 20*10/2 = 25 + 100 = 125 square centimeters.5

Use the built in Google calculator to perform the necessary calculations. For example, to calculate a search

**area**of a right triangle according to the example of the fourth step, it is necessary to enter a search query: "10^2 / 4 + 20*10/2", and then press the Enter key.# Advice 3: How to find the lateral surface area of a cylinder

Calculate the lateral surface area of a cylinder it is necessary in different situations. For example, you want to sew cushion cover-cushion and you need to determine the fabric consumption. Or are you going to paint round the barrel and have to calculate the amount of paint. Maybe your goal is to Wallpaper the walls in a round room? In all these cases, you will be faced with the task to determine the area of the lateral surface of the cylinder.

You will need

- Calculator, roulette or the tape

Instruction

1

The lateral surface of the cylinder in the expanded view is a rectangle.

The formula for calculating the area of the cylinder surface is simple:

Bok = LхH

where Bok — the desired lateral surface area of a cylinder.

The right part of the equality represented by the product of the two multipliers:

L is the measured length of the circumference of the cylinder, H is its height.

In turn, the circumference at the base of the cylinder is calculated by the formula:

L=PI x D

where PI — the number PI is a constant and is equal to 3.1416

D — diameter circle at the base of the cylinder.

A practical method of determining the area of the cylinder surface is chosen according to circumstances.

The formula for calculating the area of the cylinder surface is simple:

Bok = LхH

where Bok — the desired lateral surface area of a cylinder.

The right part of the equality represented by the product of the two multipliers:

L is the measured length of the circumference of the cylinder, H is its height.

In turn, the circumference at the base of the cylinder is calculated by the formula:

L=PI x D

where PI — the number PI is a constant and is equal to 3.1416

D — diameter circle at the base of the cylinder.

A practical method of determining the area of the cylinder surface is chosen according to circumstances.

2

Write down all your existing data on the cylinder, the lateral surface area which you need to determine.

If you know the height and diameter of the cylinder, then simply substitute in the formula for these parameters. Knowing the height and diameter of promotional stands, we can calculate the size of the poster. It is absolutely not necessary to see and measure cylindrical pedestal, on which is placed the poster.

If you know the height and diameter of the cylinder, then simply substitute in the formula for these parameters. Knowing the height and diameter of promotional stands, we can calculate the size of the poster. It is absolutely not necessary to see and measure cylindrical pedestal, on which is placed the poster.

3

Take a tape measure or measuring tape to determine the circumference of a circle at the base of the cylinder, if the cylinder is unknown.

In the absence of a flexible measuring tool you can do any rope, twine or braid. The circumference of the base of the cylinder define with a rope. The resulting segment of the rope, measure any measuring tools, such as tailor's ruler.

In the absence of a flexible measuring tool you can do any rope, twine or braid. The circumference of the base of the cylinder define with a rope. The resulting segment of the rope, measure any measuring tools, such as tailor's ruler.

4

Define the height of the cylinder.

When measuring the height of the cylinder, it is important to adhere strictly to the vertical to obtain an accurate result. To define the line vertical also useful for rope, the ends of which is tied to any load. For example, conventional nuts. One end of the rope attach to the base of the cylinder. Rope under the weight of the load is strictly vertical position. Along the line vertical and should be measure the height of the cylinder.

Multiply the two received measurements of the parameter. The result of the multiplication is the lateral surface area of a cylinder.

When measuring the height of the cylinder, it is important to adhere strictly to the vertical to obtain an accurate result. To define the line vertical also useful for rope, the ends of which is tied to any load. For example, conventional nuts. One end of the rope attach to the base of the cylinder. Rope under the weight of the load is strictly vertical position. Along the line vertical and should be measure the height of the cylinder.

Multiply the two received measurements of the parameter. The result of the multiplication is the lateral surface area of a cylinder.

# Advice 4: How to find the area, knowing the diameter

Objectives to calculate the area of a circle often meet in the school geometry course. To find the

**area**of a circle, you need to know the length**of the diameter**or radius of a circle in which it is enclosed.You will need

- - the length of the diameter of the circle.

Instruction

1

A circle is a figure in the plane consisting of a plurality of points disposed in the same distance from another point called the centre. A circle is a flat geometric figure, represents the set of points enclosed in a circle which is the boundary of the circle. Diameter is a segment that connects two points on the circle and passing through its center. The radius is the segment connecting a point on the circle and its center. π — the number "PI", a mathematical constant that is the constant. It shows the ratio of the circumference to the length of its

**diameter**. To compute the exact value of π is impossible. In geometry use the approximate value of this number: π ≈ 3,142

The area of a circle equals the product of the square of the radius to the number calculated by the formula: S=NR^2, where S is

**the area**of the circle, R is the length of the radius of the circle.3

From the definition of the radius, it follows that it is equal to half

**the diameter**. Hence, the formula becomes: S=π(D/2)^2, where D is the length**of the diameter**of the circle. Substitute in the formula the value**of the diameter**, calculate**the area**of a circle.4

The area of a circle is measured in square units — mm2, cm2, m2, etc. In what units is expressed you received

**the area**of a circle depends on what units was the diameter of a circle.5

If you need to calculate

**the area**of a ring use this formula: S=π(R-R)^2, where R, r are radii of the outer and inner circumferences of the ring, respectively.Useful advice

There is an international day of "PI", which is celebrated on March 14. The exact time of onset of the official date — 1 hour 59 minutes 26 seconds, according to figures the number is 3,1415926...