Circles Review for Flashcard

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 r is the radius and d is the diameter.

Front

What is the radius of a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

What is the diameter of a circle?

Back

The diameter is twice the radius; it is the distance across the circle through its center.

Front

What is the relationship between radius and diameter?

Back

Diameter = 2 × Radius.

Front

How do you convert the area of a circle from square units to a different unit?

Back

Use conversion factors based on the units involved (e.g., 1 cm² = 100 mm²).

Front

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

Back

Area = π(7)² ≈ 153.94 cm².

Front

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

Back

Radius = Circumference / (2π) ≈ 5 cm.

Front

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

Back

Circumference = π × 10 cm ≈ 31.4 cm.

Front

What is the area of a circle with a radius of 5 cm?

Back

Area = π(5)² ≈ 78.54 cm².