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AREA AND PERIMETER
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Area and Perimeter
These two topics are a bit like second cousins, and they can be every bit as
annoying. In fact they can be like second cousins who are twins and who
wear the same outfits to your house every Christmas. Not as annoying as
Jedward, but a close second.
The important thing to remember is not to confuse them. When you see a
question that looks like it could be a perimeter or area question read the
question carefully to see which category it falls into.
There may possibly be a question which asks both, we’ll practise for these but
generally it will be one or the other. Ok enough about those annoying cousins
let’s see what we need to know.
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Perimeter
Simply put this is the distance around an object. Think football fields, your
playground, using a trundle wheel on a cold January morning counting
clicks!!!
First we need to find the length of each side by
Counting the squares.
8 cm
6
cm
6 cm
8 cm
The perimeter of the shape is 8 + 6 + 8 + 6 = 28cm.
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Mark where you are to start
As you count the sides write the lengths in the form of a sum
Add up the lengths carefully
Check the answer to make sure it is the correct form of units: cm, mm
etc.
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AREA
Area is the space inside a shape or object. Think back to colouring in squares
in a Maths workbook, this is area.
There are a few different ways that an exam can test area. This is the first.
To find out how much shape is inside we can
Count the squares.
AREA is
the space
inside!!
The area of the shape is 18cm2.
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Tick each square as count.
Add up the ticks
Check once before moving on
That’s it. That’s area taken care of. Now if only life was that simple.
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The second type of question involves irregular shapes. In these questions
there isn’t an exact answer. The person who will mark your test will be given a
range of answers from which they can give a mark. So if you follow the
correct method you will get the mark.
This is an irregular
shape. This means
that the sides aren’t
straight.
Look out for the
word estimate:
this means
there is a range
of answers
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I would recommend starting in the top left hand corner and work across
from left to right.
If a square is half or more tick it.
Work across the row.
Then move down to the next row and continue as before.
Now go back and count the ticks carefully.
Check once before moving on.
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This needs to be practised quite a few times to ensure you understand how to
do these problems effectively.
Area simply is the amount of space that a 2-d object takes up.
You can be 99% sure that an area question will rear its head in a test so it’s
really important to make sure you can calculate areas. This is an examiners
favourite.
We can work out the area of a rectangle
Using the formula Length × Breadth
Length
Width
Area = length x width
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Write the equation length times breadth= area
Then fill in the relevant measurements from the digram you are given
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Simply multiply the length by the breadth
Check your answer to see if the examiner wants it changed to a
different unit
Remember the answer to a squared calculation must contain the
squared symbol. You will most likely be given it but in the case of
anyone taking the AQE tests make sure that if it isn’t there write it in.
The formula can be re-arranged if you know the area
Length = Area ÷ width
Width = Area ÷ length
I’m not sure, but I would say that the people who make up the tests must like
gardening in their spare time. This is another firm favourite of theirs. You
have to find the area of the path.
Mmmm, just had a lovely
idea for those tests in
November!!!!
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Don’t worry they didn’t bet on the transfertutor being around to thwart their
cunning plans!!!
Area of a Border = Total Area – Inside Area
1m
Total area = 12m x 6m = 72m2
Inside area = 4m x 10m = 40m2
6m
Border = 72m2 – 40m2 = 32m2
12
To find the inside rectangle’s dimension subtract 2 off the length and 2 off the
breadth of the larger square.
Ok these are probably the trickiest. We call these compound shapes.
Compound words are called compound words because they are made from
two words. In the same way compound shapes are made from two shapes.
To work out the total area of compound shapes you must split the shape into
2 parts or even three parts. We then find the area of each of the three shapes
and then add them back together. Simple isn’t it??
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5cm
Total area = 60 + 40 = 100cm2
2cm
12cm
4cm
Area =
5 x 12
Area =
4 x 10
60cm2
40 cm2
10cm
To find the area of
this shape we
have to split it up
into two
rectangles.
9cm
A shape that is
made from other
shapes is known
as a compound
shape.
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4cm
2cm
9cm
Area =
4x 9
36cm
Area =
4x5
4cm
5cm
2
20cm2
4cm
2cm
4cm
Total area = 36 + 20 = 56 cm2
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If faced with a compound shape
First divide the shape with a line
Next take the first shape and find its length and breadth
Multiply and find the area
Now do the same for the other shape
Add the two calculations together
Check your unit of measurement
I personally find that with these types of area questions you need to complete
10-15 of them before you really get to grips with them. Ok what are you
waiting for????????????????????????????
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