 # Area and Perimeter

I have put a couple of tasks on here that you can either print out at home and complete or you can view online and use your workbook to complete. The tasks also have the answers available so you can check your own work (no cheating please! )

These are objectives that are on the Year 5 Maths curriculum but MyMaths did not have a task to match. I have put a little explanation with each task and links to other websites that may help too.

Area of Irregular Shapes

When finding the area of an irregular shape, it is important to remember that when you are finding the area of anything, you are trying to find how many squares, of whatever unit of measurement

(mm, cm, m, km) fit into that space or shape. This, for example, is not a regular shape, but is made up of 11 full squares. If it was made up in cm squares, then the area would be 11 cm squared.

Here it is asking for square units so would be 11 square units. The total area here is made up of some full squares but some with only a fraction of each square filled.

These type of irregular shapes will have to have an estimated area.

How can I do that?

1. Count the completely full and covered squares first.

Here there are only 2.

2. Then count ones that are over 3/4 full as also whole.

Here there are 3.

3. Then count ones that are half or just over half full. Two of these squares will add to make a full one.

Here there are perhaps two that you may count as just over half and put them together to make 1.

4. Put together as best you can, small parts that would make a whole square.

The five sqaures that are less than half full, you could count as one in total!

So all together we would have 6cm squared.

Another option is to simply just count squares that are halfway or over as 1 and then the other small parts will have already been accounted for.

These two YouTube teaching clips (USA) explain the matching to make whole squares with diagrams and drawings to help you! They are worth a watch before you try the activity!

Finding the Perimeter of Rectilinear Shapes

Oooo! That sounds complicated. It does, but if I just explain it means a shape made up of rectangles

(like and 'L') then it sounds a little easier to understand!

We know, from last week, and what you remember from previous years, that the perimeter is finding the measurement of all the way around the outside of a shape. I like to imagine myself at a point of one of the shapes, and then I walk along every edge, until I come back to where I started. The distance I walked would be the perimeter.

With rectilinear shapes, I may just have some more edges to walk around and total up! So here, I would start at the blue point (bottom right) and move in a clockwise direction.

Along 8cm, then up 8cm, then across 4cm, then down 5cm, then across 4cm and then down 3cm to stop as I have come to where I started!

So the perimeter will be 8+8+4+5+4+3

You should have as many numbers as sides!

So the perimeter is:

32 cm

Sometimes things are not always quite so easy, and you may not have the length written down for every side. You have to use what you know about the other sides to try and work out the missing pieces.

This may help here! There are questions at the end. You can try if you like, but I have not added the video that shows the answers!