L.O. To find areas of squares and rectangles in cm² or m².

Draw an 8 by 5 rectangle on a squared background. What is its area? Do we need to count the squares in every row? Why not? Sketch a rectangle and label the sides 7cm and 3cm. If the sides were 7cm and 3cm, how many square centimetres would be inside this rectangle? Remember that we can multiply the length by the breadth.

If our hall was having a new floor and the price was based on its area, how could we work out the area? Would we measure it in square centimetres? No, the hall’s length and width would be measured in metres, and so the area would be in square metres.

Look at the following measurements: 12m², 120m², 12cm², 28cm², 12mm², 28mm². Which of these could be the area of a bedroom floor? The surface area of a little finger nail? One side of a credit card?

Activity 

Draw as many rectangles as you can with a perimeter of 48cm on squared paper. Then find the area of each. As an additional challenge, find the maximum and minimum possible areas. You can do this on plain paper too, it is just a bit trickier.

You may need to check that you are clear about the difference between area and perimeter. The perimeter is measuring the distance AROUND the shape; the area is measuring the space INSIDE the shape. 

e.g. A rectangle that is 10cm x 5cm 

The perimeter would be 10 + 10 + 5 + 5 = 20cm 

The area would be 10 x 5 = 50cm²