Circle Formulas and Applications

The video tutorial covers the concepts of area and circumference of circles. It begins with an introduction to the formulas for area (πr²) and circumference (2πr or πd), using 3.14 as an approximation for π. The tutorial provides step-by-step examples of calculating the area and circumference of circles, emphasizing the importance of identifying whether a radius or diameter is given. It also includes problem-solving exercises to find the diameter or radius when given the circumference. The tutorial concludes by highlighting the relevance of these concepts for understanding volume in future lessons.

What is the formula for the area of a circle?

• pi r squared

• pi times d

• 2 pi r

• r squared

If the radius of a circle is 12 meters, what is the area?

• 150 square meters

• 144 square meters

• 452.16 square meters

• 314 square meters

What is the area of a circle with a diameter of 35 kilometers?

• 961.625 square kilometers

• 385 square kilometers

• 700 square kilometers

• 1234 square kilometers

Which formula would you use if you are given the diameter of a circle to find the circumference?

• r squared

• pi times d

• 2 pi r

• pi r squared

A circle has a diameter of 18 inches. What is its circumference using pi as 3.14?

• 56.52 inches

• 113.04 inches

• 28.26 inches

• 36 inches

What is the circumference of a circle with a radius of 7 meters using 2 pi r?

• 43.96 meters

• 21.98 meters

• 14 meters

• 28 meters

If a circle has a radius of 15.6 cm, what is its circumference?

• 31.2 cm

• 78.54 cm

• 49.2 cm

• 97.968 cm

If a circle's circumference is 65.97 meters, what is its diameter?

• 23 meters

• 20 meters

• 22 meters

• 21 meters

What is the radius of a circle with a circumference of 21.99 feet?

• 4 feet

• 2.5 feet

• 3.5 feet

• 3 feet

Why is it important to understand area and circumference formulas?

• They are used in algebra.

• They are only used in geometry.

• They are used in calculating volume.

• They are not important.