Area & Circumference of Circles

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius of the circle.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr or Circumference = πd, where d is the diameter.

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Front

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

Back

154 cm² (Area = π(7)² = 154 cm²).

Front

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

Back

5 cm (Circumference = 2πr, so r = 31.4/(2π) = 5 cm).

Front

What is π (pi)?

Back

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

Front

How do you find the radius if you know the diameter?

Back

Radius = Diameter / 2.

Front

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

Back

78.5 cm² (Area = π(5)² = 78.5 cm²).

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius.

Front

If a circle has an area of 100 cm², what is the radius?

Back

Approximately 5.64 cm (Area = πr², so r = √(100/π)).