7.9B Circumference and Area of Circles Flashcard

Front

What is the formula for calculating the circumference of a circle?

Back

Circumference = π × diameter or Circumference = 2 × π × radius.

Front

What is the formula for calculating the area of a circle?

Back

Area = π × radius².

Front

If the diameter of a circle is 16 cm, what is the radius?

Back

Radius = diameter ÷ 2 = 8 cm.

Front

What is the approximate value of π?

Back

π is approximately 3.14.

Front

How do you convert diameter to circumference?

Back

Multiply the diameter by π.

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 cm)² ≈ 78.5 cm².

Front

If a circular garden has a radius of 3 m, what is its area?

Back

Area = π × (3 m)² ≈ 28.3 m².

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × radius.

Front

How do you find the area of a circle if you only know the circumference?

Back

First, find the radius using the formula radius = circumference ÷ (2 × π), then use Area = π × radius².