Area of a Circle

LC: Derive formula in finding the area of a circle.

I. Learning Objectives: After the activity, pupils shall be able to:
C: derive area formula of a circle.
P: determine the area of a circle using the formula A = ∏ x r2
A: finish the assigned task within the given time frame.

II. Learning Content:
Topic: Area of a Circle
Concept: A = ∏ x r2
Values: sense of responsibility
Materials: paper plates, scissors
Resources: Apistar, E. (2005), Soaring 21st Century
Torres, H. (2009) Number Smart
http://www.education.com/activity/fourth-grade/page7/

III. Learning Experience:
Classroom Routine - checking of attendance, ID, etc.
A. Introduction:
1. Preview:
a. Motivation: Show a circle drawn on centimeter grid
- How many squares are there inside the circle?
b. Presentation of the day’s lessons.

B. Interaction:
Work with a group!
1. Fold your paper plate into eights.
2. Unfold the plate and cut along the creases
3. Arrange the pieces to form a parallelogram as shown below.

a. What is the height of the parallelogram?
b. What is the length of the parallelogram’s base?
c. How would you find the area of the parallelogram?
d. How would you find the area of the circle?
e. What is the formula for it?

Area = base x height = 1/2 circumference x radius = 1/2 [(pi) x 2r] r = (pi)x r2
C. Integration:
1. Generalization:
o How do we derive for the area formula of a circle?

2. Valuing:
· How do you show your sense of responsibility to your groupmates?

3. Action: Find the area of a circle using the formula:
d = 5 in
r =10 in


IV. Evaluation: Criteria
Solution:
10 points – solution is complete, clear, and correct.
5 points – solution is correct but style of presentation is poor.
3 points – solution is incorrect

Teamwork: 5 pts. – each member of the group performs the task
3 pts – 50% of the group performs the task

V. Assignment: ½ crosswise
a. Explain how the area of a parallelogram is related to the area of the
circle?
b. Write in your own words, how to find the area of a circle with a
diameter of 6m.