Because the radius of a circle is equal to twice its diameter, these equations are essentially the same. The units for circumference can be any unit for the measure of length: feet, miles, meters, centimeters, etc.
The radius (r) of a circle is the distance from one point on the circle to the center of the circle. The diameter (d) of a circle is the distance from one point on the circle to another directly opposite it, going through the circle’s center. [7] X Research source The Greek letter pi (π) represents the ratio of the circumference divided by the diameter and is represented by the number 3. 14159265…, an irrational number that has neither a final digit nor a recognizable pattern of repeating digits. [8] X Research source This number is commonly rounded to 3. 14 for basic calculations.
In most textbook math problems, the radius or diameter is given to you.
For example: What is the circumference of a circle with a radius of 3 cm? Write the formula: C = 2πr Plug in the variables: C = 2π3 Multiply through: C = (23π) = 6π = 18. 84 cm For example: What is the circumference of a circle with a diameter of 9 m? Write the formula: C = πd Plug in the variables: C = 9π Multiply through: C = (9*π) = 28. 26 m
Find the circumference of a circle with a diameter of 5 ft. C = πd = 5π = 15. 7 ft Find the circumference of a circle with a radius of 10 ft. C = 2πr = C = 2π10 = 2 * 10 * π = 62. 8 ft.
Because the radius of a circle is equal to half its diameter, these equations are essentially the same. The units for area can be any unit for the measure of length squared: feet squared (ft2), meters squared (m2), centimeters squared (cm2), etc.
The radius (r) of a circle is the distance from one point on the circle to the center of the circle. The diameter (d) of a circle is the distance from one point on the circle to another directly opposite it, going through the circle’s center. [15] X Research source The Greek letter pi (π) represents the ratio of the circumference divided by the diameter and is represented by the number 3. 14159265…, an irrational number that has neither a final digit nor a recognizable pattern of repeating digits. [16] X Research source This number is commonly rounded to 3. 14 for basic calculations.
In most textbook math problems, the radius or diameter is given to you.
For example: What is the area of a circle with a radius of 3 m? Write the formula: A = πr2 Plug in the variables: A = π32 Square the radius: r2 = 32 = 9 Multiply by pi: A = 9π = 28. 26 m2 For example: What is the area of a circle with a diameter of 4 m? Write the formula: A = π(d/2)2 Plug in the variables: A = π(4/2)2 Divide the diameter by 2: d/2 = 4/2 = 2 Square the result: 22 = 4 Multiply by pi: A = 4π = 12. 56 m2
Find the area of a circle with a diameter of 7 ft. A = π(d/2)2 = π(7/2)2 = π(3. 5)2 = 12. 25 * π= 38. 47 ft2. Find the area of a circle with a radius of 3 ft. A = πr2 = π32 = 9 * π = 28. 26 ft2
For example: Calculate the circumference of a circle with a radius of (x = 1).
For example: Calculate the circumference of a circle with a radius of (x + 1). Write the formula: C = 2πr Plug in the given information: C = 2π(x+1)
For example: Calculate the circumference of a circle with a radius of (x = 1). C = 2πr = 2π(x+1) = 2πx + 2π1 = 2πx +2π = 6. 28x + 6. 28 If you are given the value of “x” later in the problem, you can plug it in and get a whole number answer.
Find the area of a circle with a radius of 2x. A = πr2 = π(2x)2 = π4x2 = 12. 56x2 Find the area of a circle with a diameter of (x + 2). A = π(d/2)2 = π((x +2)/2)2 = ((x +2)2/4)π
