Look at this shape which is made of two rectangles joined together.
There is a 6 cm by 2 cm rectangle lying flat and a 3 cm by 7 cm rectangle lying upright.
We can use the fact that rectangles have parallel sides of equal length to work out missing distances in rectangular arrangements.
Example 1
In the diagram above, work out the length a in cm.
Answer
Use the fact that the top rectangle is 2 cm tall all the way along, even at its right-hand edge.
Also the upright rectangle is 7 cm tall even at its left-hand edge.
This is shown in the diagram below.
This means that a is 7 cm – 2 cm = 5 cm.
Example 2
In the diagram, work out the length a in cm.
Answer
Use the fact that the top of the blue rectangle will match the length of the bottom as 4 cm.
The length a will be 7 cm + 4 cm.
This is shown in the diagram below.
This means that a is 7 cm + 4 cm = 11 cm.
