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 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.**