You will need

- The compass
- The concept of radius, diameter and circumference
- The formula for the circumference of a circle

Instruction

1

Remember what the length

**of the circumference**and how is it measured. In practical life this is usually used flexible measuring devices like a tape or tape measure. If you need to know**the diameter of the**cylinder base, you can make it scan, circling the base and building side surface. The length**of the circumference**of the base in this case will be equal to the length of the base.2

Remember, what is the formula to calculate the length of the

**circumference**. Indicate the length**of a circle**With radius as R,**the diameter**— as D. the Length**of a circle**is equal to twice the product of the radius by the number ?, C=2?R. Remember what**the diameter****of the circle**. This is twice the radius.3

Find twice the radius

**of the circle**. 2R=C/?. Thus, D=C/?. Remember, what is the number ?. It is equal to 3, 14. Divide the length**of the circumference**by this number. To determine the necessary radius of the resulting quotient divided by 2. Will watertite a circle according to the obtained radius.4

Knowing the length of the radius, one can determine the area of a circle. You must do this if making a pattern round the hat, you want to calculate. How much material is needed. Indicate the area of the circle as S. It will be equal to the number ?, multiplied by the square of the radius.

Note

The number p is an infinite decimal. It is usually rounded off to two digits after the decimal point.

The radius is calculated to the required accuracy. If it turns out an infinite decimal, it is interrupted in the hundredths or tenths and rounded.

The radius is calculated to the required accuracy. If it turns out an infinite decimal, it is interrupted in the hundredths or tenths and rounded.