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## 'Finding Factors' printed from http://nrich.maths.org/

The interactivity below is similar to the one used in

Missing
Multipliers so you may wish to work on that first.

In the multiplication grid below, the headings and the answers
have been hidden. Each of the headings is an expression of the form
$x \pm a$ where $a$ is an integer between $0$ and $5$. By revealing
some of the answers, can you work out what each heading must
be?

Drag the green and purple labels
onto the headers to make the correct expressions. If you change
your mind, you can remove a label by clicking on it.
This text is usually replaced by the Flash movie.

What is the smallest number of answers you need to reveal in order
to work out the missing headers?

Can you describe a strategy for completing the Level 3 challenge
consistently?

Once you have a strategy for completing Level 3, try this slightly
more challenging version:

This text is usually replaced by the Flash movie.