Practice: Circumference and Area of Circles

Front

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

Back

The circumference (C) of a circle can be found using the formula: C = 2πr, where r is the radius.

Front

What is the relationship between the diameter and radius of a circle?

Back

The diameter (d) of a circle is twice the radius (r): d = 2r.

Front

How do you calculate the area of a circle?

Back

The area (A) of a circle can be calculated using the formula: A = πr², where r is the radius.

Front

What is the value of π (pi)?

Back

π (pi) is approximately equal to 3.14 or can be expressed as the fraction 22/7.

Front

If a circle has a radius of 5 cm, what is its circumference?

Back

Using the formula C = 2πr, the circumference is C = 2π(5) = 10π cm.

Front

If a circle has a diameter of 12 inches, what is its radius?

Back

The radius is half of the diameter, so the radius is 12/2 = 6 inches.

Front

Which expression represents the circumference of a circle with a radius of 7 cm?

Back

The expression is C = 2π(7) = 14π cm.

Front

What expression could NOT be used to find the circumference of a circle with a radius of 4.5 cm?

Back

The expression 4.5π cannot be used because it does not account for the formula C = 2πr.

Front

If the radius of a circle is 3 cm, what is the area?

Back

Using the formula A = πr², the area is A = π(3)² = 9π cm².

Front

What is the diameter of a circle with a radius of 8 cm?

Back

The diameter is d = 2r, so d = 2(8) = 16 cm.