Area of a Circle
Topic: Measurement (Area of a Circle)
Grade 5 (4th Quarter)
Goal: the students should be able to demonstrate understanding of the area of a circle in real life situations
Objectives:
At the end of a session, the students should be able to:
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visualize the area of a circle;
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derive a formula in finding the area of a circle;
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find the area of a given circle; and
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solve mathematical problems and real-life situations involving the area of a circle.
Materials:
LCD projector, pen, paper, handouts, Manila paper, tape, puzzle pieces
Resources:
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Area of a Circle. (n.d.). Retrieved March 18, 2018, from https://www.mathsisfun.com/geometry/circle-area.html
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Area of a Circle. (n.d.). Retrieved March 18, 2018, from http://www.aaamath.com/geo612x2.htm
Motivation:
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The class will be divided into 4.
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Each group will receive puzzle pieces.
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Within 2-3 minutes, each group should solve the puzzle pieces.
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After 3 minutes, each group will describe what picture they have got.
Lesson Procedure:
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The teacher will recall their past discussion about circles using the motivational activity.
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The teacher will give students a handout of a plain circle. The teacher will instruct the class to it cut it like the pictures shown below. After cutting it like that, further cut the wedges into 2 which make it a total of 8 and cut it again making it look like the second picture.
3. After the activity, the teacher will ask, "When the circle is divided into wedges and arrange like this, does it look like another shape you know? What do you think would happen if we kept dividing the wedges and arranging them like this?" The teacher will lead the discussion so students realize the shape currently resembles a parallelogram, but as it is continually divided, it will more closely resemble a rectangle.
4. After it, the teacher will further ask, "What are the dimensions of the rectangle that is formed?" From the previous lesson, students should realize that the length of the rectangle is equal to half the circumference of the circle, or πr. Additionally, it should be obvious that the height of this rectangle is equal to the radius of the circle, r. Consequently, the area of this rectangle is πr × r = πr^2. Because this rectangle is equal in area to the original circle, this activity gives the area formula for a circle:
A = πr^2
Assessment
Performance Task
