Lesson 4 - Area and perimeter

Lesson 4 - Area and perimeter

Learning intentions - Use the correct formula to accurately calculate area and perimeter

Bronze - To be able to find the area & perimeter of rectangles, triangles, parallelograms and trapeziums.

Silver and Gold - To be able to find the area & perimeter of compound shapes.

Poll

How confident are you at calculating area and perimeter of different shapes?

• Really confident (5/5)

• Pretty confident (4/5)

• I'm OK at doing it (3/5)

• Unconfident (2/5)

• I really struggle with this topic (1/5)

What are area and perimeter?

• Area is the space occupied by a shape.

• Perimeter is the distance around a shape.

Multiple Choice

The distance around a shape is its _____________.

• area

• perimeter

Multiple Choice

The __________ is the space occupied by a shape.

• area

• perimeter

Calculating the perimeter of a shape

• Calculating the perimeter of a shape is the easier of the two.

• To do this, you would need to add together all of the lengths of the sides of the shape.

Multiple Choice

What is the perimeter of the rectangle?

• 14 feet

• 28 feet

• 48 feet

• 2 feet

What is the perimeter of the rectangle?

• To work this out, you need to add all of the sides together

• That would be 8 + 6 + 8 + 6 to give you 28 feet.

Multiple Choice

What is the missing measurement? 

• 9 cm
• 18 in
• 18 cm
• 9 in 

What is the missing measurement? 

• This is sometimes how questions are presented in examination.

• You would need to know that for a rectangle, the opposites are the same distance.

• This would mean that the missing measurement is 18cm.

Multiple Choice

What is the perimeter of this polygon?

• 39 in
• 24 in
• 105 in 

What is the perimeter of this polygon?

• Questions won't always be about square or rectangles

• Much like those, you would still need to add together all of the sides which would be 15 + 15 + 9 = 39 inches

Multiple Choice

What is the perimeter of the shaded figure?

• 28
• 24
• 22
• 26

What is the perimeter of the shaded figure?

• Some questions may not come with measurements but with blocks for you to count.

• In this image, the height is 4 and the length is 7.

• Adding up all the sides, the perimeter should be 22.

Multiple Choice

A football field is 300 feet long. If the perimeter of the field is 920 feet, what is the width?

• 620 feet

• 320 feet

• 160 feet

• 310 feet

A football field is 300 feet long. If the perimeter of the field is 920 feet, what is the width?

• This question expects you to know what the shape of a football field is - a rectangle.

• If the length is 300 feet and you know there will be 2 lengths, you should be able to subtract 600 from 920 to give you 320 feet.

• This is the distance of 2 widths, so you need to divide this by 2 to get a distance of 160 feet.

Calculating the area of squares and rectangles

• When calculating the area for squares and rectangles, all you need to do is mutliply the length by the width.

• Something to remember is that the answer will always be (squared) when looking at an area.

Multiple Choice

Find the area of this rectangle.

$Area\ =length\times width$

• $14\ m^2$

• $28\ m^2$

• $48\ m^2$

• $96\ m^2$

Find the area of this rectangle.

• To find the area, you multiply the length by the width.

• 8 x 6 = 48m squared.

Fill in the Blank

The area of this rectangle is _____ square units.

The area of this rectangle is _____ square units.

• Again, to find the area of the square, you should multiply the length by the width.

• 10 x 3 = 30 squared (no units supplied)

Fill in the Blank

Mya built a rectangular flower garden. The garden is 10 feet long and 8 feet wide.

What is the area of Mya’s flower garden?

$Area=length\times width$

Mya built a rectangular flower garden. The garden is 10 feet long and 8 feet wide. What is the area of Mya’s flower garden?

• This would mean that you need to multiply 10 feet by 8 feet.

• This would make an area the size of 80 feet squared.

Finding the area of different shapes

• Many different shapes can be asked and the all have different ways of working out the area.

• Check out the video to see how to calculate the areas.

As a reminder, these are the calculations that you need to remember!

Multiple Choice

Check out the image of the Triangle . 

The base= b=14in ,height h= 8in. Find the Area of the Triangle using the formula:  $\frac{1}{2}b\cdot h\ \ or\ \ \frac{b\cdot h}{2}$  

• A=56 squared inches

• A=112 squared inches

• A= 28 squared inches

• A=  65 squared inches

The b=14in, h= 8in. Find the Area of the Triangle.

• Step 1 - Divide the base by 2 - 14/2 = 7

• Step 2 - Multiply this number by the height - 8x7 - 56

• Step 3 - Add the units - inches ²

Multiple Choice

Check out the image of the parallelogram. The base b=6m and height h=5m. Find the Area of the parallelogram using the formula: A= bh

• A= 300m²

• A=11m²

• A=180m²

• A=30m²

What is the area of the parallelogram?

• Step 1 - Multiply the height by the base - 5x6 = 30

• Step 2 - Add the units - metres ²

Multiple Choice

Area of triangle?

• 17 units²
• 20 units²
• 10 units²
• 16 units²

Find the area of the triangle

• Step 1 - Divide the base by 2 - 5/2 = 2.5

• Step 2 - Multiply this number by the height - 4 x 2.5 = 10 units ²

Multiple Choice

Find the area.

• 30 in²

• 60 in²

• 21 in²

• 50 in²

Find the area of the parallelogram

• Step 1 - Multiply the base by the height - 5x10 = 50

• Step 2 - Add the units - inches ²

Multiple Choice

Find the area of the trapezium

• 40cm²

• 80cm²

• 60cm²

• 160cm²

Find the area of the trapezium

• This is a typical question and really difficult!

• Step 1 - Add the top and the bottom values together - 6+10 =16

• Step 2 - Divide this value by 2 - 16/2 = 8

• Step 3 - Multiply this value by the height - 8x5 = 40

• Step 4 - Add in the units - cm²

When do we use area and perimeter in real life?

• In everyday life area and perimeter are used constantly – for example, for describing the size of a house by talking about its floor area, or for working out how much wire is needed to fence off a field.

Multiple Choice

The farmer needs to cover with soil a garden that measures 6m by 5m. Each bag of soil covers 10 square meters. How many bags of soil will he need?

• 30 bags

• 11 bags

• 3 bags

• 22 bags

Bags of soil...

• Step 1 - Find the area - 6m x 5m = 30m²

• Step 2 - Divide the area by the amount of soil in each bag - 30/10 = 3 bags

Poll

How confident are you at calculating area and perimeter of different shapes after this session?

• Really confident (5/5)

• Pretty confident (4/5)

• I'm OK at doing it (3/5)

• Unconfident (2/5)

• I really struggle with this topic (1/5)

Exit ticket

Fantastic work! Be sure to head over to your Microsoft Teams page for Maths and find the Microsoft Forms quiz on the 'assignments' tab. 

If you complete this quiz, that will act as your register for this session. No completed quiz - no mark!