area and circumference of circles

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd, where C is the circumference, r is the radius, and d is the diameter.

Front

What does 'π' represent in circle formulas?

Back

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

Front

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

Back

A = π(7)² = 49π cm², approximately 153.94 cm².

Front

If the diameter of a circle is 10 m, what is its circumference?

Back

C = πd = π(10) = 10π m, approximately 31.42 m.

Front

What is the relationship between radius and diameter?

Back

The diameter is twice the radius: d = 2r.

Front

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

Back

r = √(A/π), where A is the area.

Front

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

Back

A = π(5)² = 25π in², approximately 78.54 in².

Front

What is the circumference of a circle with a radius of 4 feet?

Back

C = 2π(4) = 8π ft, approximately 25.13 ft.

Front

If a circle has a circumference of 20 cm, what is its radius?

Back

r = C/(2π) = 20/(2π) = 10/π cm, approximately 3.18 cm.