Circle- Area and circumference

What is the formula for circumference of a circle given the diameter?

• C = π r

• C = 2 π r

• C = π d

• C = 2 π d

Answer explanation

The formula for the circumference of a circle given the diameter is C = πd, where C represents the circumference and d is the diameter.

The _____ is the distance from the center to any point on the circle.

• diameter

• radius

• π

• center

Answer explanation

The radius is the distance from the center to any point on the circle, making it the correct choice.

The distance across a circle through its center is called the _____.

• diameter

• radius

• π

• center

Answer explanation

The distance across a circle through its center is called the diameter, which is the correct choice among the options provided.

If you are given the diameter, how can you calculate the radius?

• Multiply the diameter by 2

• Divide the diameter by 2

• Add 2 to the diameter

• Subtract 2 from the diameter

Answer explanation

To calculate the radius from the diameter, you need to divide the diameter by 2, as the radius is always half of the diameter.

Daniel wants to buy cookies for her friend. The
radius of a cookie is 5 inches. What is the cookie’s 
circumference?   Use C=2πr
Pi = 3.14

• 10 in

• 2.5 in

• 15.7 in

• 31.4 in 

Answer explanation

The circumference of a circle is calculated using the formula C = 2πr. Substituting r=5, C = 2*3.14*5 = 31.4 in. Therefore, the correct answer is 31.4 in.

What is the formula for Circumference?

• C = π×r²

• C = 2×π×r

Answer explanation

The formula for Circumference is C = 2×π×r, which represents the distance around a circle. This formula is derived from the definition of circumference as the ratio of the circle's diameter to its radius.

What is the radius of this circle?

• 12cm

• 6cm

• 24cm

• 3cm

Answer explanation

The radius of the circle is 6cm because it is the distance from the center to any point on the circumference.

What is π ? (Best Choice)

• The ratio of the circumference of any circle to its diameter.

• Exactly 3.14

• Exactly 3.1415

• Exactly 3.141593

Answer explanation

The ratio of the circumference of any circle to its diameter is the definition of π, making it the best choice among the options provided.

What is the formula for area of a circle?

• A = π×r²

• A = 2×π×r

Answer explanation

The formula for the area of a circle is A = π×r². This means the area is equal to pi times the radius squared.

What is the area of this circle?

• 62.59 cm²

• 113.1 cm²

• 19.81 cm²

• 28.26 cm²

Answer explanation

The correct answer is 28.26 cm^2, which is the area of the circle calculated using the formula A = πr^2.