E-Portfolio

Topic: Circumference

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Grade 5, Quarter 4

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Goal: The students will be able to demonstrate understanding circumference

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Objectives:

 At the end of the lesson, students will be able to:

1. define what circumference is;

2. derives a formula in finding the circumference of a circle; and

3. finds the circumference of a circle in real objects.

           

Materials

LCD projectors, tape measure, manila paper, marker, powerpoint presentation.

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Resources

Circumference of Circle retrieved from https://www.mathopenref.com/circumferencederive.html

What is the circumference of a circle retrieved from https://www.youtube.com/watch?v=2fC6vxszhHk

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Motivation:

1. The class will be divided into 3 groups.

2. Each group will be given a material kit containing a paper and a pen.

3. Each group will be instructed to explore the hallway (of their classroom) and find circular objects. Draw it on the paper as many as they can find.

4. After 6-8 minutes, they will go back to the classroom and discuss the objects they have drawn.

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Lesson Procedure

1. After the motivational activity, the teacher will ask the following questions:

• Do you know that circles just like polygons also have perimeter?

• Does anyone know how do we call the perimeter of a circle?Introduce that the distance/length around the circular object is called the circumference.

  2. The teacher will relate that the circumference is actually the perimeter of a circle. The distance across the circular object is called the diameter and half the diameter is called the radius.

The teacher will present the equation of pi (π) to the class: π = 3.1415926535 or simply 3.14.

  3. The teacher will then discuss that  is the ratio of the circumference of a circle to the diameter. Thus, for any circle, if you divide the circumference by the diameter, you get a value close to. This relationship is expressed in the following formula:

 

C/d = π

 

  4. Given the value of pi, the teacher will ask the class to derive the formula for circumference. The teacher will then call 2-3 students to explain their work.

  5. After the student/s discuss their work, the teacher will supplement further and end the lesson proper saying C= π x d as the formula of the circumference and since the radius is half the diameter, circumference can also be solved through C= π x 2 x r.

 

Assessment

Answer the following questions.

1. What is the circumference of a circle with a diameter of 4.5 cm?

2. A round wooden table has a radius of 2 m.  Find its circumference.

3. Give the circumference of a clock with 9 inches as its diameter.

4. You are a gardener. A round flower plot needs to be fenced with wire.  If it measures 9 m across, how long should be the wire needed to fence around the plot?

5. The distance around a circular running field is 75 m. If you are a runner and you want to run across the field, how far would your run be?

 

Performance Task