You will certainly remember indigenous Grade 6 the perimeter is the distance around the outermost border that something. Area is the dimension of a flat surface the something. In this chapter, friend will find out to use various formulae to calculation the perimeter and also area that squares, rectangles and triangles. You will certainly solve difficulties using these formulae, and you will likewise learn just how to convert between different systems of area.

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Perimeter the polygons

The perimeter that a form is the full distance around the shape, or the lengths of its sides included together. Perimeter (P) is measure in systems such together millimetres (mm), centimetres (cm) and metres (m).

Measuring perimeters

Use a compass and/or a leader to measure up the size of every side in figures A come C. Write the dimensions in mm on every figure.

compose down the perimeter of every figure.


The following shapes consist of arrows that space equal in length.

What is the perimeter of each form in number of arrows?

If each arrowhead is 30 mm long, what is the perimeter the each shape in mm?


Perimeter formulae

If the political parties of a square room all \(s\) units long:

\<\beginalign \textbfPerimeter that square &= s+ s+s+s\\ &= 4 \times s\\ \textor p &= 4s\endalign\>


If the length of a rectangle is \(l\) units and also the breadth (width) is \(b\) units:

\<\beginalign \textbfPerimeter of rectangle &= l+l+b+b\\ &=2\times l + 2 \times b\\ \textor P&=2(l+b) \endalign\>


A triangle has three sides, so:

\<\beginalign \textbfPerimeter that triangle &= s_1 + s_2 + s_3\\ \textor p &= s_1 + s_2 + s_3 \endalign\>


Applying perimeter formulae

calculation the perimeter of a square if the length of among its political parties is 17,5 cm.

One next of an it is intended triangle is 32 cm. Calculate the triangle"s perimeter.

Calculate the size of one next of a square if the perimeter that the square is 7,2 m. (Hint: \(4s\ =\) ? therefore \(s =\) ?)

Two political parties of a triangle are 2,5 centimeter each. Calculate the length of the 3rd side if the triangle"s perimeter is 6,4 cm.

A rectangle is 40 cm long and also 25 cm wide. Calculate its perimeter.

calculate the perimeter that a rectangle the is 2,4 m large and 4 m long.

The perimeter the a rectangle is 8,88 m. How long is the rectangle if it is 1,2 m wide?

perform the essential calculations in her exercise book in stimulate to finish the table. (All the dimensions refer to rectangles.)







74 mm

30 mm

25 mm

90 mm


1,125 cm

6,25 cm


5,5 cm

22 cm


7,5 m

3,8 m

2,5 m

12 m

Area and also square units

The area of a form is the dimension of the level surface surrounded by the border (perimeter) that the shape.

Usually, area (A) is measure up in square units, such together square millimetres (mm2), square centimetres (cm2) and square metres (m2).

Square units to measure up area

Write under the area of numbers A come E below by counting the square units. (Remember to include halves or smaller components of squares.)


each square in the grid listed below measures 1 cm2 (1 cm \(\times\) 1 cm).

What is the area that the shape drawn on the grid?

on the very same grid, attract two forms of her own. The shapes should have actually the very same area, however different perimeters.


Conversion of units

The figure listed below shows a square with sides that 1 cm.The area that the square is one square centimetre (1 cm2).

How numerous squares the 1 mm by 1 mm (1 mm2) would certainly fit right into the 1 cm2 square? ______ Complete: 1 cm2 = _______ mm2

To change cm2 come mm:2

1 cm=2 1 centimeter \(\times\) 1 cm

= 10 mm \(\times\) 10 mm

= 100 mm2

Similarly, to readjust mm2 to cm2:

1 mm2 = 1 mm \(\times\) 1 mm

= 0,1 cm \(\times\) 0,1 cm

= 0,01 cm2

We have the right to use the same technique to convert in between other square devices too. Complete:

From m2 to cm2:

\< \beginalign 1 \text m^2 &= 1 \text m \times 1 \text m \\ &=\text______ cm \times \text______ cm\\ &=\text______ cm^2 \endalign\>

From cm2 come m2:

\< \beginalign 1 \text cm^2 &= 1 \text cm \times 1 \text cm \\ &=0.01 \text m \times 0.01\text m\\ &=\text______ m^2 \endalign\>

So, come convert between m2, cm2 and mm2 you execute the following:

cm2 come mm2 \(\rightarrow\) multiply by 100 m2 come cm2 \(\rightarrow\) multiply by 1000 mm2 to cm2 \(\rightarrow\) divide by 100 cm2 come m2 \(\rightarrow\) division by 10000

Do the necessary calculations in your practice book. Then fill in her answers.

15 m2 = ______ cm2 5 cm2 = ______ mm2 20 cm2 = ______ m2 20 mm2 = ______ cm2 25 m2 = ______ cm2 240 000 cm2 = ______ m2 460,5 mm2 = _______ cm2 0,4 m2 = ______ cm2 12 100 cm2 = ______ m2 2,295 cm2 = ______ mm2

Area that squares and also rectangles

Investigating the area that squares and rectangles

Each of the following four figures is split into squares of same size, specific 1 centimeter by 1 cm.

Give the area of each figure in square centimetres (cm2):

Area the A:

Area the B:

Area of C:

Area that D:

Is over there a shorter method to occupational out the area of every figure? Explain.

figure BCDE is a rectangle and MNRS is a square.


How plenty of cm2 (1 cm \(\times\) 1 cm) would fit into rectangle BCDE?

How plenty of mm2 (1 mm \(\times\) 1 mm) would fit right into rectangle BCDE?

What is the area of square MNRS in cm2?

What is the area the square MNRS in mm2?

Figure KLMN is a square with sides of 1 m.

How many squares with sides that 1 cm would certainly fit along the size of the square?

How numerous squares v sides that 1 cm would certainly fit follow me the breadth that the square?

How countless squares (cm2) would thus fit right into the whole square?

Complete: 1 m2 = ______ cm2

A quick means of calculating the number of squares that would certainly fit into a rectangle is to multiply the number of squares that would certainly fit along its length by the variety of squares that would certainly fit follow me its breadth.

Formulae: area of rectangles and squares

In the rectangle top top the below: \< \beginalign \textNumber that squares &= \textSquares along the length \times \textSquares along the breadth \\ &= 6 \times 4 \\ &= 24 \endalign\>


From this we can deduce the following:

\< \beginalign \textbfArea the rectangle &= \textLength that rectangle \times \textBreadth of rectangle\\ A &= together \times b\endalign\> where \(A\) is the area in square units, \(l\) is the length and also \(b\) is the breadth)

\< \beginalign \textbfArea that square &= \textLength of side \times \textLength of side\\ A &= l \times together \\ &=l^2 \endalign \> where \(A\) is the area in square units, and \(l\) is the length of a side)

The systems of the values used in the calculations need to be the same. Remember:

1 m = 100 cm and 1 centimeter = 10 mm 1 cm2 = 1 cm \(\times\) 1 cm = 10 mm \(\times\) 10 mm = 100 mm2 1 m2 = 1 m \(\times\) 1 m = 100 centimeter \(\times\) 100 centimeter = 10 000 cm2 1 mm2 = 1 mm \(\times\) 1 mm = 0,1 cm \(\times\) 0,1 centimeter = 0,01 cm2 1 cm2 = 1 centimeter \(\times\) 1 centimeter = 0,01 m \(\times\) 0,01 m = 0,0001 m2 instances

calculation the area of a rectangle v a length of 50 mm and a breadth of 3 cm. Provide the prize in cm2.


\< \beginalign \textArea the rectangle & = together \times b & & &\\ &= (50 \times 30) \text mm^2& \text or A &= (5 \times 3)\text cm^2\\ &= 1 500 \text mm^2 & \text or & = 15 \text cm^2 \endalign \>

calculation the area of a square bathroom tile with a side of 150 mm.

Solution: \< \beginalign \textArea of square tile &= together \times l \\ &=(150 \times 150) \text mm^2\\ &= 22500\text mm^2\\ \endalign\>

The area is thus 22 500 mm2 (or 225 cm2).

calculate the size of a rectangle if the area is 450 cm2 and also its width is 150 mm.

Solution: \< \beginalign \textArea that rectangle & = l \times b & & &\\ 450 &= together \times 15 & & &\\ 30 \times 15 &= together \times 15 & \text or 450 \div 15& = l\\ 30 = l & & 30 &= l\\ \endalign \>

The size is as such 30 centimeter (or 300 mm).

Applying the formulae

Calculate the area of each of the adhering to shapes:

a rectangle v sides of 12 cm and 9 cm

a square v sides the 110 mm (answer in cm2)

a rectangle v sides that 2,5 cm and also 105 mm (answer in mm2)

a rectangle v a length of 8 cm and a perimeter the 24 cm

A rugby field has a size of 100 m (goal write-up to score post) and also a breadth that 69 m.

What is the area that the field (excluding the area behind the score posts)?

What would certainly it cost to plant new grass on that area in ~ a expense of R45/m2?

Another unit for area is the hectare (ha). It is mainly used because that measuring land. The dimension of 1 ha is the equivalent of \( 100 \textm \times 100 \textm\). Is a rugby field greater or smaller than 1 ha? explain your answer.

perform the essential calculations in your exercise publication in bespeak to finish the table. (All the dimensions refer to rectangles.)






8 m

120 m2


120 mm


60 cm2


3,5 m

4,3 m



2,3 cm


2,76 cm2


5,2 m

460 cm


figure A is a square with sides of 20 mm. The is cut as shown in A and also the components are combined to form figure B. Calculation the area of figure B.

What is the area that the vegetables patch?

She tree carrots on half of the patch, and also tomatoes and potatoes ~ above a quarter of the patch each. Calculation the area extended by each kind of vegetable?

How lot will she salary to put fencing roughly the patch? The fencing expenses R38/m.

grandfather Allie has to tile a kitchen floor measure \(5 \textm \times 4 \textm\). The blue tiles he supplies each measure \(40 \textcm \times 20 \textcm\).

How many tiles does grandfather Allie need?

The tiles are offered in crate containing 20 tiles. How countless boxes should he buy?

Doubling a side and also its impact on area

When a side of a square is doubled, will the area the the square likewise be doubled?

The dimension of each square consisting of the grid listed below is \(1 \textcm \times 1 \textcm\).

For every square attracted on the grid, label the lengths the its sides.

Write under the area of every square. (Write the answer within the square.)

Notice the the second square in every pair the squares has a side size that is double the side length of the an initial square.

Compare the locations of the squares in every pair; then finish the following: once the next of a square is doubled, its area


Area the triangles

Heights and bases that a triangle

The height (h) of a triangle is a perpendicular line segment drawn from a vertex come its opposite side. The contrary side, which develops a best angle through the height, is referred to as the base (b) of the triangle. Any kind of triangle has three heights and three bases.


In a right-angled triangle, 2 sides are already at best angles:


Sometimes a base must be extended outside the the triangle in order to attract the perpendicular height. This is displayed in the an initial and 3rd triangles below. Note that the extended part does not form part the the base"s measurement:


Draw any type of height in every of the adhering to triangles. Label the elevation (h) and base (b) on every triangle.

Label another set of heights and bases on every triangle.


Formula: area of a triangle

ABCD is a rectangle with size = 5 cm and also breadth = 3 cm. Once A and also C space joined, the creates two triangles that space equal in area: \(\triangle ABC\) and \(\triangle ADC\).


\(\textArea the rectangle = together \times b\)

\< \beginalign \textArea the \triangle abc \text (or \triangle ADC\text) &= \frac12 \text(Area that rectangle)\\ &= \frac12(l \times b) \endalign \>

In rectangle ABCD, advertisement is that is length and CD is its breadth.

But look at \(\triangle ADC\). Have the right to you check out that ad is a base and CD is that height?

So rather of saying:

Area the \(\triangle ADC\) or any type of other triangle \(= \frac12(l \times b)\)

we say:

\< \beginalign \textbfAre that a triangle &= \frac12 \text(base \times \textheight)\\ &=\frac12(b \times h)\\ \endalign \>

In the formula because that the area of a triangle, b way "base" and also not "breadth", and also h means perpendicular height.

Applying the area formula

usage the formula to calculate the locations of the adhering to triangles: \(\triangle ABC\), \(\triangle EFG\), \(\triangle JKL\) and also \(\triangle MNP\).



PQST is a rectangle in each instance below. Calculation the area the \(\triangle PQR\) every time.


R is the midpoint of QS.

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In \(\triangle ABC\), the area is 42 m2, and also the perpendicular height is 16 m. Uncover the size of the base.