Flashcard 7- Area and Circumference of a Circle

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, where r is the radius of the circle.

Front

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

Back

Area = π(10)² = 314.16 cm² (approximately).

Front

If the radius of a circle is 12.5 mm, what is its circumference?

Back

Circumference = 2π(12.5) = 78.54 mm (approximately).

Front

What is the value of π (pi) to two decimal places?

Back

π ≈ 3.14.

Front

How do you convert the radius to diameter?

Back

Diameter = 2 × radius.

Front

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

Back

Diameter = 2 × 5 m = 10 m.

Front

If a circular garden has a circumference of 31.4 m, what is its radius?

Back

Radius = Circumference / (2π) = 31.4 / (2π) ≈ 5 m.

Front

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

Back

Area = π(4)² = 50.27 cm² (approximately).

Front

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

Back

Circumference = π × 20 in ≈ 62.83 in.