PERIMETER AND AREA

Students` Learning Outcomes

• Recognize region of a closed figure.
• Differentiate between perimeter and area of a region.

Information for Teachers

• First clear the concept of open and closed ended shapes then the concept of perimeter and an area.
  

 

• Closed ended shapes are those shapes closed from starting to end point like rectangle, square, triangle etc. while drawing a shape if you start and end at same point the shape is closed.
• Open ended shapes are those shapes having no end points. While drawing the shape if you start and end at two different points, the shape is open like crescent moon, arch etc.
• We can find the perimeter of an open end shape but not its area.
  

 

 

• Perimeter is the total distance around the outside of a shape. Perimeter can be measured in meters and centimetres.
• Area is the amount of region that a two dimensional shape covers. It is measured in square units. Some of these units are square centimetres, square meters and square kilometers. We calculate the area of a square or rectangle by multiplying its length and breadth and perimeter can be measured by adding length of all the sides.
• Perimeter of an open end shapes as shown in figure can be found but we can`t find the area of open end shapes.
• Shaded part is and “area” and part outside is called “perimeter”.
  

 

 

• Consult text book at all steps wherever required.

 

Material / Resources

Writing board, chalk / marker, duster, pencil, paper, ruler, scissors, chart paper cutouts with different shapes and sizes

Introduction

• Close the door of the room
• Ask the students:

§  Can you go out of the room if the door is closed?

§  Now open the door and ask:

§  Can you go out now?

• Draw an open and a closed shape on the board.
  

 

• Now ask which one of these shapes is like a room with a closed door and which one is is like a room with an open door?
• Give reasons for your answer.
• Explain the concept of open end and closed end shapes.
• By drawing different shapes on the board ask them to differentiate between closed and open end shapes.

 

Development

Activity 1

Whole Class Activity:

• Draw different figures open and closed end shapes on the board.
  

 

• Call different students and ask them to identify which shape is ‘open ended’ or which is ‘closed ended’?
• Ask students to give reasons for their answers.
• Check if they find any difficulty in differentiating the shapes.
• Repeat the concept once again.
• Ask them to define open and closed shapes.
• After they have tried tell them the correct definition.

 

Group Work:

• Split class into groups.
• Give a worksheet with different shapes to each groups to identify which shape is open and which is closed ended. Or
• Ask the groups to draw different open and closed shapes and explain why they are open or closed?
• Allocate time (15 minutes)
• Call one student from each group to come and tell the whole class which shape is closed or which one is open with reason.

Activity 2

• Draw square on the board and ask them to suppose that this is a square field and we have to make a fence around it. How much fence will we need if one side of the field is 12 meters?
  

 

• Let them think of for a while and then help them to conclude that we will add all 4 sides 12 + 12 + 12 + 12 = 48 m
• Ask why it is important to know the perimeter of shapes. Ask them to discuss in pairs and give reasons.
• Ask the students to focus on the inside region of the square. Tell them that the inside region of the square is called the area of the square. It is measured in square units.
• Draw another square and label each side as 2 meter.
• Divide the square into 4 equal squares. Ask what is the length of side of each of the smaller square? [1 meter]
• How many 1 meter squares are in this big square?
• Conclude that the area of the bigger square is 4 square meters.
• Repeat the activity by drawing different squares and rectangles on the board and talking about their area and perimeter.

 

Sum up / Conclude

• If the start and end points of a figure are same, then it is called a Closed Figure.
• At least three lines or sides are required to form a closed polygon.

• All the figures shown above are closed figures as their start and end points are same.
• Perimeter is the total distance around the outside of a shape. Perimeter can be measured in meters and centimetres.
• The perimeter of the rectangle shown in AB + BC + CD + DA = 8 + 5 8 + 5 = 26 units.
  

 

• Perimeter of a rectangle can also be found using the formula 2(l + w), where l is the length and w is the width.

 

Assessment

Individual Work:

• Assign questions from the textbook to be done individually and record for assessment.
• Draw different shapes on the board and ask them to differentiate as open or closed.
• Involve the students in solving the problems given at the end of the lesson of text book.

Follow up

• Ask them to find perimeter of things in their house like their bed or table etc.
• Assign Worksheets for Home Work
• Q. 1: Measure the perimeter of these shapes?  

 

• Q. 2: Match each shape to its perimeter.