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## 'Mystery Matrix' printed from http://nrich.maths.org/

Have a look at this table square or matrix:

Can you see how it has been constructed?

Why are some numbers in black and some in red?

Can you explain why the red $6$ is in that particular square?

Why is there a $45$ in the bottom right-hand corner?

You will notice that the numbers $2$ - $9$ are used to generate the matrix and only one of these numbers is used twice (the $2$).

Can you fill in the matrix (table square) below?

The numbers $2$ -$12$ were used to generate it with, again, just one number used twice.

Click here for a poster of this problem.