Area of regular and irregular shapes

This term we have been focusing on Area of 2D regular and irregular shapes.

To begin with we discussed as a class what we thought Area meant.

Area is the size of a surface of a 2D shape.ย 

It is also very important to make sure you have the correct units of measurement when calculating area of shapes. Mrs Baldwin asked us if anybody knew what units of measurement we would use for area. After a few conversations we realised that we needed to make sure we had ‘squared’ at the end of our area answers. For example…

If a shape has an area of 12cm2 this means that the surface can be covered by 12 squares that are 1 centimetre on each side.

square-cm

If a shape had an area of 350m2 which is how a lot of blocks of land or houses area measured in, this means that the surface of that shape can be covered by 350 squares that are 1 metre on each side.

square-m

We then looked at how we can calculate the area of regular shapes by placing a shape on a grid and counting the squares inside of shape.

area-grid

 

If each square was 1cm on a side then the area would be 15cm2

Next we discussed how to use the grid paper to calculate the area of irregular shapes. We all drew our hands on a grid of paper. Mrs Baldwin then set the task to find a strategy that best suited us to calculate the total area of our hand. This was a great challenge and it was interesting to see the many different types of strategies. Once we found the answer we were asked to explain how we solved this underneath our working out.

A few of us had an opportunity to share with the class our different ways of calculating the answer. Some of us used coloured pencils and coloured in the whole squares first and then matched the half squares together to make wholes, some of us placed numbers in each square so we could keep track of our counting. A lot of us had to use our knowledge of fractions with adding squares together that were broken in halves and also quarters. Check out some of our solutions below…

img_0240 img_0241 img_0242 img_0243 img_0244 img_0245 img_0246 img_0247 img_0248

The following lesson Mrs Baldwin asked us how we could calculate the area of a regular shape without using grid paper. Imagine trying to measure the area of our classroom floor using the squares from our maths books! This would take a very long time!!

We discovered that there is a formula to calculate area of rectangle and square shapes. The formula is

Area = Length x Width.

 

area-rectangle

Some of us were also able to complete more challenging irregular shapes. With these shapes we had to find a way to cut the shapes so that they would become rectangles or squares. We would then calculate the area of both shares and then add both of these answers together to get the total area.

area_of_irregular_shapes

However sometimes we were given irregular shapes where we had to figure out the length or width of one of the sides by using the other dimensions. For example

area10

If we drew a horizontal line to create a long thin rectangle along the bottom and the other shape becomes a square we would have to think carefully what the length and width would be for both shapes in this case.

 

Check out the video below for more information about Area.

 

Next is using all these skills to create our ver own dream house!

What did you learn about calculating area of different shapes?

When in everyday life do you think you would need to calculate the area of something? Provide an example.

Can you find the area of the 2 shapes below. Make sure you use the correct units of measurement.

9by4mm area10

3 thoughts on “Area of regular and irregular shapes

  1. hey class of 2016 it’s Finn! ๐Ÿค‘

    i loved doing the hand thingy it was really fun! I didn’t finish mine but i had a good try

    sorry but i have to work on my spelling now bye! Finn๐Ÿ˜Ž

  2. Hey miss Baldwin.๐Ÿ˜ƒ

    I thought it was very fun to do the hand maths thingy because it was challenging to do it.

  3. Dear Mrs Baldwin,
    I learnt that you can find the area of any shape,
    I think you would need to find the area of a room in a house and it would have to be at lest 15m2 for a bedroom,
    the top shape is 36mm2 & the bottom one is 27cm2

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