Circles

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is the relationship between diameter and radius?

Back

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

Front

How do you calculate the circumference of a circle?

Back

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

Front

What is the value of π (pi) approximately?

Back

π is approximately 3.14.

Front

If the radius of a circle is 7 cm, what is the area?

Back

A = π(7)² = 153.9 cm² (rounded to the nearest tenth).

Front

What is the diameter of a circle with a radius of 4 inches?

Back

The diameter is 8 inches (d = 2r).

Front

If the area of a circle is 50.3 m², what is the radius?

Back

r = √(A/π) = √(50.3/π) ≈ 4.0 m.

Front

What is the area of a circle with a diameter of 10 feet?

Back

A = π(5)² = 78.5 feet².

Front

What does it mean if a circle has a radius of 0?

Back

The circle is a point with no area.

Front

How do you convert diameter to radius?

Back

Divide the diameter by 2 (r = d/2).