Circumference of a Circle

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd, where C is circumference, r is radius, and d is diameter.

Front

What does the symbol π (pi) represent?

Back

Pi (π) is a mathematical constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

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

Back

C = 2πr = 2 × π × 10 cm ≈ 62.8 cm.

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius (d = 2r).

Front

What is the circumference of a circle with a diameter of 20 cm?

Back

C = πd = π × 20 cm ≈ 62.8 cm.

Front

What is the distance around a circle called?

Back

Circumference.

Front

If the circumference of a circle is 31.4 cm, what is the radius?

Back

r = C/(2π) = 31.4 cm / (2π) ≈ 5 cm.

Front

What is the area of a circle with a radius of 7 cm?

Back

A = πr² = π × (7 cm)² ≈ 153.94 cm².

Front

How do you convert circumference to diameter?

Back

d = C/π.

Front

What is the circumference of a circle with a radius of 5 m?

Back

C = 2πr = 2 × π × 5 m ≈ 31.4 m.