Circles and Pi

Calculate the circumference of a circle with a radius of 8 units. (Use π = 3.14)

• 25.12

• 64.32

• 50.24

• 40.48

Answer explanation

The question asks to calculate the circumference of a circle with a radius of 8 units using π = 3.14. The formula for the circumference is C = 2πr. Substituting the given values, we get C = 2 * 3.14 * 8, which equals 50.24. So, the correct option is 50.24.

What is the formula to calculate the circumference of a circle?

• 2 * radius

• pi * radius

• radius * radius

• 2 * pi * radius

Answer explanation

The question asks for the formula to calculate the circumference of a circle. The correct formula is '2 * pi * radius'. In this formula, '2' is the multiplier, 'pi' is a constant approximately equal to 3.14, and 'radius' is the distance from the center of the circle to its edge. Therefore, to find the circumference, you multiply twice the value of pi by the radius.

What is the radius of a circle if its diameter is 10 units?

• 5

• 7

• 2.5

• 12

Answer explanation

The question asks for the radius of a circle given that its diameter is 10 units. In circle geometry, the radius is exactly half of the diameter. Therefore, if the diameter is 10 units, then the radius would be 5 units. Hence, the correct answer is 5.

How is Pi defined?

• The ratio of the diameter of a circle to its circumference

• The ratio of the circumference of a circle to its diameter

• The ratio of the radius of a circle to its circumference

• The ratio of the circumference of a circle to its radius

What is the definition of pi?

• The ratio of a circle's circumference to its diameter

• The ratio of a circle's radius to its diameter

• The ratio of a circle's area to its diameter

• The ratio of a circle's circumference to its are

What digits do we use for Pi?

• 3.14

• 31.4

• 314

What number is pi?

• 41

• 00

• 3.14

• 5.14

What is the value of Pi (π)?

• 3.14159

• 3.1416

• 22/7

• 3.14

Answer explanation

The value of Pi (π) is approximately equal to 3.14159, which is a mathematical constant used to represent the ratio of a circle's circumference to its diameter. While other options are close approximations, 3.14159 is the most accurate value listed.

What is the significance of Pi in circle calculations?

• Pi is used to calculate the volume of circles.

• Pi is used to calculate the angles of circles.

• Pi is used to calculate the diameter of circles.

• Pi is used to calculate the circumference, area, and other properties of circles.

Answer explanation

Pi (approximately 3.14159) is a mathematical constant representing the ratio of a circle's circumference to its diameter. It plays a crucial role in calculating various properties of circles, such as circumference (C = 2 * Pi * r) and area (A = Pi * r^2), where 'r' is the radius of the circle. The other options mentioned are not the primary uses of Pi in circle calculations.

Calculate the area of a circle with a diameter of 12 units. (Use π = 3.14)

• 37.68

• 144

• 113.04

• 6.28

Answer explanation

To calculate the area of a circle, we use the formula A = πr², where A is the area and r is the radius. The given diameter is 12 units, so the radius is 6 units. Using π = 3.14, the area is calculated as A = 3.14 * (6²) = 3.14 * 36 = 113.04 square units, which is the correct answer.