Area and Perimeter of Circles

Lesson 18 focuses on solving complex problems involving the area and circumference of circles. The video covers calculating the area of semicircles, quarter circles, and composite shapes like placemats. It also includes practical applications such as determining fabric requirements and perimeter for sewing projects. The lesson emphasizes using known formulas and adapting them to new situations.

What is the essential question addressed in this lesson?

• How to calculate the volume of a sphere?

• How to determine the surface area of a cube?

• How to solve complex problems on area and circumference of circles?

• How to find the perimeter of a rectangle?

Which formula is used to find the area of a semicircle?

• PI R squared

• PI R squared divided by two

• 2 PI R

• PI D

If the diameter of a semicircle is 14 cm, what is its radius?

• 7 cm

• 21 cm

• 14 cm

• 28 cm

How do you calculate the area of a quarter circle?

• PI D divided by four

• 2 PI R

• PI R squared divided by two

• PI R squared divided by four

What is the radius of a quarter circle if its diameter is 12 cm?

• 12 cm

• 6 cm

• 24 cm

• 3 cm

In the placemat design, what shapes are combined to find the total area?

• One rectangle and one circle

• One square and one triangle

• Two rectangles

• Two circles

If each square on the grid measures 4 inches, what is the radius of the circle in the placemat design?

• 8 inches

• 16 inches

• 4 inches

• 2 inches

What is the formula for the perimeter of a circle?

• PI R squared

• 2 PI R

• PI D

• R squared

How much band material is needed to go around the edge of one placemat?

• 49.12 inches

• 25.12 inches

• 12 inches

• 8 inches

What is the total area of six placemats if one placemat has an area of 146.24 square inches?

• 146.24 square inches

• 438.72 square inches

• 877.44 square inches

• 292.48 square inches