3 by 3 step stair

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Andrew Belcher

This is a 3 by 3 step stair, this is because the step stair goes up by three squares and down by three squares. We will call this step stair ‘S-number 1’ as that is the number in the bottom left of the step stair. The step stair total (which we will call the S-total) is all the numbers within the step stair added together. The step stair total for this step stair for example is 50, as 1+2+3+11+12+21=50

I am now going to try and find an algebraic equation for finding the S-total from the S-number. I am now going to find a link between the S-number (which we will call N) and the rest of the numbers in the grid:

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N+20

N+10  N+11

N        N+1    N+2

I can now work out a general by adding together all the N’s:

N+N+N+N+N+N= 6N

And then adding that to all the other numbers added together:

10+20+11+1+2=44

There for the algebraic rule is 6N+44

I can prove this by using the S-number 1. If you put 1 in the formula it is 6x1+44, which gives us 50. If you add 1+2+3+11+12+21 it also gives you 50, so the rule works.

I will prove it again with another example. If you put the ...

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