Circles (7.9B, 7.9C, 7.5B)

Front

What is the definition of a circle?

Back

A circle is a shape consisting of all points in a plane that are a fixed distance (radius) from a central point (center).

Front

What is the formula for the diameter of a circle?

Back

The diameter (d) of a circle is twice the radius (r): d = 2r.

Front

What is the value of pi (π)?

Back

Pi (π) is approximately 3.14159 and represents the ratio of the circumference of a circle to its diameter.

Front

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

Back

The diameter is 14 cm (d = 2r).

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) of a circle is given by the formula C = 2πr.

Front

What is the area of a circle with a radius of 3 cm?

Back

The area (A) is approximately 28.27 cm² (A = πr²).

Front

What is a semicircle?

Back

A semicircle is half of a circle, formed by cutting a whole circle along its diameter.

Front

If a circle has a diameter of 10 m, what is its radius?

Back

The radius is 5 m (r = d/2).

Front

What is the relationship between radius and diameter?

Back

The radius is half the diameter: r = d/2.

Front

How do you find the circumference of a semicircle?

Back

The circumference of a semicircle is half the circumference of a full circle plus the diameter: C = πr + d.