Circles - Area, Circumference, Radius & Diameter Explained!

If the diameter of a circle is 10 cm, what is its radius?

• 5 cm

• 10 cm

• 20 cm

• 15 cm

Answer explanation

The radius of a circle is half of its diameter. Given the diameter is 10 cm, the radius is 10 cm ÷ 2 = 5 cm. Therefore, the correct answer is 5 cm.

Tags

CCSS.7.G.B.4

Match each term related to a circle with its correct definition.

• Area

• The area of the circle

• Diameter

• The diameter of the circle

• Circumference

• The distance around the circle

• Radius

• The distance from the center to the edge

Which of the following is true about the area of a circle?

• It's always larger than the circumference.

• It is measured in linear units.

• It can be calculated as A = 2\pi r.

Answer explanation

The area of a circle is calculated using the formula A = πr², where r is the radius. This is the correct choice, as the other options either misstate the area or confuse it with the circumference.

Tags

CCSS.7.G.B.4

What is the relationship between the diameter and the radius?

• The diameter is half of the radius.

• The diameter is equal to the radius.

• The diameter is twice the radius.

• The diameter has no relationship to the radius.

Answer explanation

The diameter of a circle is defined as twice the length of the radius. Therefore, if you know the radius, you can find the diameter by multiplying it by 2.

Tags

CCSS.7.G.B.4

How do you find the area of a circle with a radius of 7 cm?

• A = 7\pi

• A = 14\pi

• A = 2\pi(7)

Answer explanation

To find the area of a circle, use the formula A = πr². With a radius of 7 cm, substitute r with 7: A = π(7²) = π(49). Thus, the correct choice is A = π(7²).

Tags

CCSS.7.G.B.4

Which of the following formulas is used to calculate the diameter of a circle?

• d = 2r

• d = \pi r

• d = 2\pi r

Answer explanation

The correct formula to calculate the diameter of a circle is d = 2r, where d is the diameter and r is the radius. This means the diameter is twice the length of the radius.

Tags

CCSS.7.G.B.4

What is the area of a circle with a diameter of 12 m? (this is a multi step answer)

• 36\pi

• 144\pi

• 12\pi

• 144

Answer explanation

To find the area of a circle, use the formula A = πr². The diameter is 12 m, so the radius r = 12/2 = 6 m. Thus, A = π(6)² = 36π. Therefore, the area is 36π, which is the correct choice.

Tags

CCSS.7.G.B.4

Which of the following statements is true regarding circles?

• All circles have the same circumference.

• The area of a circle increases with the square of its radius.

• The radius is always greater than the diameter.

• The circumference can be calculated by C = 2r.

Answer explanation

The area of a circle is calculated using the formula A = πr², which shows that the area increases with the square of the radius. The other statements are incorrect regarding circles.

Tags

CCSS.7.G.B.4

The area of a circle is calculated using which formula?

• A = 2πr

• A = πd

• A = 2r

Answer explanation

The area of a circle is calculated using the formula A = πr², where r is the radius. This formula derives from the relationship between the radius and the area, making it the correct choice.

Tags

CCSS.7.G.B.4

The circumference of a circle can be found using the formula (a)  

• C = 2πr

• C = πd

Answer explanation

The circumference of a circle is calculated using the formula C = 2πr, where r is the radius. This formula shows that the circumference is directly proportional to the radius, making it the correct choice.

Tags

CCSS.7.G.B.4