E2020 answer keys

area is 1/2 of the diameter time 3.1415 squared= area
example diameter is 10 of 1/2 of 10 is 5 so 5 x5=25
25 x 3.1415 = 69.133 Radius is 1/2 of diameter
diameter is 2 time the radius
example Radius is 5 so 2(twice) radius (5) is 10
example diameter = 10 so .5 (1/2) is 5
Circumference is pi (3.1415) time diameter.
.example diameter is 10 so 3.14515 x 10= 31.45
https://www.calculatorsoup.com/calculators/geometry-plane/circle.php

It sounds like you are trying to determine the surface area of a cylinder.

The area of the top and the bottom of the cylinder (which are circles) are pi x r ^ 2. Since there are two of them, we have to multiply this answer by 2.

The surface area of the side is going to be the circumference of the circle times the height. The circumference is 2 x pi x r and the height is 15 inches.

To get the total surface area, we have to add these amounts together.

Good luck,

Paul

area formula is PI x r squared
that is 3.1417 times the radius of the circle squared
example is:- 3.1417 times 3 inches squared =3.1417 times 3x3=3.1417x9=28.279 square inches if you want to work back from a circumference measurement, the formula for circumference is 2 x PI x radius or PI x diameter
if you have a circumference of 12 inches then the dia is calculated 12 inches = dia x PI to get the diameter , divide the 12 inches by PI and that will be the diameter so that is 12 divided by 3.1417 =3.819 inches
now you can go from the first formula the radius is the diameter divided by 2 so the radius will be 3.819 divided by 2 = 1.909 inches
so applying the area formula it becomes 3.1417 times 1.909 times 1.909 =11.458 square inches
to find your answer simply substitute the dimensions in place of the example figures.in the relevant formula.

Answer is A. Divide area by pi to find the circumference. (153.86/3.14 = 49) Determine the square root of the circumference to find the radius. (sqrt of 49 = 7)

(pi)R squared (Fixya won't let me use the sign for Pi)

Area of a circle=pi*radius^2 or pi times radius times radius

example: suppose the radius of a circle is 10 inches, then the Area of the circle would be pi times 10 times 10 or 100*pi

pi represents the circumference (distance around) of a circle / diameter and for any circle is constantly the same number which is approximately 3.14

so in my example 100*pi=100*3.14 or 314 square inches

If you would like to know the circumference of a 15" diameter circle this is the formula:
circumference = radius x 2 x pi
circumference = diameter x pi

in our case:
circumference = 15" x 3,14
circumference = 47 ,1" (that's 119,634 cm)

Circumference of a Circle: 2 x pi x radius - OR - pi x diameter,

or if you need some sphere calculations?

Sphere Surface Area: 4 X pi X radius squared OR
pi X diameter squared Sphere Volume: 4/3 X pi X radius cubed OR
( pi X diameter cubed ) / 6
By the way.......... "pi" = 3.1415926536

The circumference of a circle is given by the expression
Circumference= 2* PI* Radius of circle
C=2*Pi*R
The area is given by
Area of a disk with radius R = Pi* R*R or PI*R^2
Area= PI*R^2

The formula for circumference of a circle is c=2*pi*r, using 3.14 for pi and 3.2 inches for the radius.

c=2 * 3.14 * 3.2

Good luck.

Paul

You cannot have a semicircle that has a diameter of 2.500 mm and a radius of .425mm and a circumference of 3000mm

Circumference is equal to pi times the diameter. pi is = 3.14

The radius of a circle is always 1/2 the diameter

Area of a circle is pi time the radius squared


Loringh