# Measurement of Perimeter and Area

## Measurement of Perimeter and Area

Lesson Planning of Measurement of Perimeter and Area

Subject Mathematics

Students` Learning Outcomes

• Identify the units for measurement of perimeter and area.
• Write the formulas for perimeter and area of square and rectangle.
• Apply formulas for perimeter and area of a square and rectangle.

Information for Teachers

• Any enclosed shape which doesn’t` have any open ends and it starts and ends at the same point is called closed shape.
• Shapes whose line segments don`t meet and it don`t start and end at the same point is called open ended shape.

• Distance of around the closed ended shape is called its perimeter.
• Perimeter can be measured in the units of meter, centimeter and kilometre.

• Perimeter of a shape is calculated by adding length of all of its sides.
• Area is the amount of region that a shape covers i.e. Area = Length x Breadth
• Area can be measured in square units.

Material / Resources

Writing board, chalk / marker, duster, pencil, paper, scissors, text paper, ruler, chart paper cutouts with different shapes and size etc.

Introduction

1. What is an open ended and closed ended shape?
2. What is perimeter?
3. What is area?
4. How can we measure “perimeter” and “area”?
• Discuss with the students that a perimeter and an area can be measured in m, cm, km, etc. area is measured in square units.

• Ask students to walk in the ground and identify the perimeter and an area of a ground.
• Ask students to identify and point to the perimeter and area of their pencil box, teacher`s desk, and any note book.

Development

Activity 1

• Draw the following shape on the board.
• Ask them to find out the perimeter of the shape. (Let them think and then check their answers).
• Perimeter can be measured bt adding lengths of a shape.
• Therefore the perimeter of the rectangle is 7 + 3 + 7 + 3 = 20 units.
• Ask them to draw different size shapes to find perimeters.
• Divide class into group of four members.
• Give each group drawings of different shapes of different sizes.

• Ask them to mention the name of shapes and find their perimeters.
• Make it clear that a perimeter is found by adding length of all the sides.

Activity 2

• Draw a rectangle like shape as shown on the board.
• Tell them how we will find the length of the other 2 sides.
• In a rectangle opposite sides are equal, so to work out the perimeter of a rectangle you just need to know only the length and width.
• Look at the shape and find the length of each side. Add the lengths:
• Total length of all sides is 05 + 12 + 05 + 12 = 34 NOW find the units.
• The lengths have been measured in centimetres, so the perimeter will also be measured in centimetres.
• The perimeter will be 34 centimetres.

Activity 3

• What could be the easiest way to find the perimeter of a rectangle? Help them in concluding that since the 2 opposite sides of a rectangle are equal so if we add the length and breadth and multiply the sum by 2 then we can get perimeter.

• Formula for perimeter can also be written as:
• Perimeter of a rectangle = 2 x (l + b) = 2 x 3 + 5= 16
• Where L = length and B = breadth
• Ask them to apply the formula to different rectangular shapes and verify by adding all 4 sides.
• Ask what is the perimeter of a square having side –length 74 cm?  Help them to conclude that:

• Since a square has 4 sides of equal length, the perimeter of the square is 4 + 4 + 4 + 4 = 16.Or 4 x 4 = 16.

1. What could be the easiest way to find out the perimeter of a square?
• Help them to conclude that since all 4 sides of a square are equal we can find out its perimeter by multiplying one side of the square by 4.
• So, perimeter of a square = 4 x L
• Where L = length of a side of a square.
• In above example Area = 4 x 4 =  16 cm
• Draw a square and rectangle on the board.
• Ask them to look at the shapes:
1. How many squares is each divided into (4 and 12)
• If the side of each smaller square is 1 cm how much is the area of the square?  4 cm 2 (because it has 4 small 1 cm squares)
1. What will be the area of the rectangle? 12 cm 2(because it has 12 small 1 cm squares)

Activity 5

• Ask them to find out the area of the rectangle.
• Tell them the formula for area of rectangle.

• The formula is:
• Area = L x B
• Whereas L= length and B = breadth so, we know that
• L = 5
• B = 3, so, Area = 5 x 3 = 15
• Note: the area of a figure measures the size of the region enclosed by the figure. This is usually expressed in terms of some square unit.
• A few examples of the units used are square meters, square centimetres, square inches, or square kilometres.
• The area of a rectangle is composed of its “width” and “length”. Explain few more examples to the students to make them understand about the concepts.

Area of a Rectangle:

Example 1

1. What is the area of a rectangle having a length of 6 cm and a width of 2 cm?
• The area is the product of these two sides –lengths, which is 6 x 2 = 12 cm 2.

Teacher`s Role

1. What is the area of a square having side- length 4 cm? The area is the square of the side-length, which is 4 x 4 = 16 cm 2or (4)2 = 16 cm 2.
• Explain how to find area of a square?

Example 2

• As the students to find the area of a squares in a grid
• Area can be found by counting squares in the grid.
• Total small squares inside the shape are 100. Area of a square is 100 square units.

Example 3

• Draw different grids and ask students to come and tell the units of a shape by counting squares in the grid.

Sum up / Conclusion

• Distance of around the closed ended shape is called its perimeters.
• Perimeter of a shape is calculated by adding length of all of its sides.
• Area is the amount of region that a shape covers i.e. Area = Length x Breadth
• Area can be measured in square units.

PERIMETER VS AREA

 Area Perimeter Definition: Area is the space or region occupied by a closed figure. Perimeter is the distance around a closed figure. Measurement: Square unit. Measures two dimensions e.g. 24 in2 or 24 inches squared. Measures one dimensions e.g. 24 in. or 24 inches Usage: For example to carpet the whole room. For example to put a fence around the garden. Square: s2, where s is the length of one side of the square. 4s, where s is the length of one side of the square. Rectangle: L w, where L and w are the length and width of the rectangle. 2 L + 2 w, where L and w are the length and width of the rectangle.

Formulas to calculate perimeter and area

 Shape Formula for perimeter Formula for Area Variables Square 4L L2 Where L is the side length Rectangle 2 L + 2w 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 and follow up.
• Write the following on the board and ask students to solve.
• A rectangle has sides equal to 2 cm and 7 cm find out its area and perimeter using formula.
• A square has one side equal to 8 cm so; find out its area and perimeter using formulas.s
• Involve the students in solving the problems given in the end of the lesson of textbook

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