 # How to find the area of the basis of a cylinder

If in statements of the problem it is not specified about what cylinder it is (parabolic, elliptic, hyperbolic, etc.), then the simplest option is meant. At such spatial geometrical figure in the bases circles lie, and the side surface forms with them a right angle. Calculation of parameters in this case does not represent special complexity.

## Instruction

1. If the radius (r) of the basis of a cylinder is known, then all its other sizes do not matter when calculating. Calculate the work of the number of Pi rounded to the necessary degree of accuracy on the squared radius is and there will be an area of the basis of a cylinder (S): S=π*r². For example, if diameter (it as you know, the doubled radius) a cylinder is equal to 70 cm, and the result of calculation is required to be received to within the second sign after a comma (100-th shares of centimeter), then the area of the basis will be 3.14*(70/2)² = 3.14*35² = 3.14*1225 ≈ 3848.45 cm².

2. If the radius and diameter are unknown, but height (h) and volume (V) cylinder are given, then too there will be enough these parameters for finding of the area (S) of the basis of a figure - just divide volume into height: S=V/h. For example, at the volume of equal 950 cm³ and height in 20 cm the cylinder will have the basis the area in 950/20=47.5sm².

3. If except height (h) of a cylinder the area of its side surface (p) is known, then for finding of the area of the basis (S) square the area of a side surface and divide result into the quadruple work of number of Pi on the squared height: S=p² / (4*π*h²). For example, if the area of a side surface is equal to 570 cm², then with a height of cylinder of 25 cm and the set accuracy of calculations in one 100-th centimeters it has to have the area the reasons, equal 570² / (4*3.14*25²) = 324900 / (12.56*625) = 324900/7850 ≈ 41.39 cm².

4. If except the area of a side surface of a cylinder (p) also the area of all surface (P) is known, then, having taken away from the second the first, do not forget to halve the received result as total area includes both bases of a cylinder: S=(P-p)/2. For example, if the total area of a spatial figure is 980 cm², and the area of its side surface - 750 cm², then the area of each of the bases will be equal (980-750)/2=115sm².

Author: «MirrorInfo» Dream Team