**Page 3**

Before counting quadrilaterals, we'll first start by counting smallest squares or unit squares, the size of a unit square is \(1\times 1\).

In any regular grid, the number of unit squares is \[a\times b\].

(This is quite easy to prove)

## Worked example

In the diagram above, how many unit squares are there in the grid?

**Solution:**

In any regular grid, the number of unit squares is \(a\times b\), here, \(a=3\), \(b=5\), \(a\times b=15\), so there are 15 unit squares in the grid.

This is one part of Grids and Quadrilaterals.

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