Circle Geometry and Area Concepts

Mrs. Lopez teaches grade 7 students about finding the area of a circle in lesson 17. The lesson covers the difference between calculating the area and circumference of a circle, methods to find the radius from the circumference, and how to calculate the area of a rectangle. The video includes examples and exercises to reinforce the concepts, emphasizing the importance of understanding the formulas and calculations involved.

What is the formula for finding the circumference of a circle in terms of its radius?

• πd

• r²

• πr²

• 2πr

Which method is NOT used to find the area of a rectangle?

• Multiplying length by width

• Using the formula πr²

• Multiplying side by side

• Counting the squares inside

If a rectangle has an area of 27 cm² and a width of 3 cm, what is its length?

• 3 cm

• 12 cm

• 6 cm

• 9 cm

How is the area of a circle related to the area of a rectangle in the derivation process?

• The circle is cut into triangular wedges to form a rectangle

• The circle is folded into a square

• The circle is transformed into a parallelogram

• The circle is divided into squares

What is the formula for the area of a circle?

• πr²

• r²

• πd

• 2πr

When calculating the area of a circle, why is it important to use the correct formula?

• To use fewer mathematical operations

• To make the calculation easier

• To avoid confusing it with the circumference

• To ensure the result is in square units

If a circle has a radius of 10 cm, what is its approximate area using π = 3.14?

• 31.4 cm

• 314 cm²

• 31.4 cm²

• 3140 cm²

In the problem-solving exercise, what was the error made by Joanne?

• She used the wrong value for π

• She calculated the circumference instead of the area

• She used the diameter instead of the radius

• She forgot to square the radius

What is the correct area of a circle with a diameter of 20 cm?

• 400π cm²

• 100π cm²

• 200π cm²

• 50π cm²

Why is it important to show your work when solving mathematical problems?

• To use more paper

• To ensure the teacher can follow your thought process

• To make the solution look longer

• To make the problem seem more complex