Number Stairs

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I have been given a number grid that counts in ascending order from one to a hundred, beginning at the bottom left hand corner to end at the top right corner with the number one hundred. With this grid I have been given the task of investigating the relationship/s between the grid size, the stair size, the stair total and the ‘n’ number.

The step shape given above is a 3-step stair, simply because it consists of 3 steps.

The stair total is labelled as being the sum of all of the numbers in the stair shape:

        24 + 25 + 26 + 34 + 35 + 44 = 212

                The Stair total for this 3-step shape is 212

The ‘n’ number is defined as being the smallest number of the stair shape, in the grid above it is specified as ‘ 24’.

I will systematically work my way through this problem to find appropriate algebraic solutions to simplify the workings of the stair totals. In doing so, I will use different size grids and use different size stairs. Again, investigating relationships and discovering formulae for each problem I encounter.

I am going to start with a 10 by 10 grid with a 3-step stair.

From the results I have obtained from the grid using the 3-step stair, I can clearly see a pattern developing in the ‘T’ column (‘T’ indicating the total stair number). Each number in the T column is increasing by 6 when the ‘n’ number is increased by 1.

Using the rules of n’th term I can develop an algebraic formula:

        The ‘T’ column increases by 6 each time, so we multiply the ‘n’ number by the increase:

  • 6n, and then add the remaining amount to end up with the ‘T’ number.

  • 6n + 44 = T

I will now check this formula by evaluating a sum of which I already know the solution to:

        

Using another method, I will ensure that my formula is correct and if possible simplify the expression given.

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n+n+1+n+2+ n+G+n+G+1+n+2G=T

Simplifying the above equation using means of collecting up will give me:

        6n+4G+4=T

                

                For this grid, it would be:        6n+4*10+4=T


Next I will use a 9 by 9 grid, using the same method as before to obtain an appropriate formula.

Using the same method as above, I can develop a formula.

Again, you can see that the ‘T’ column is increasing by 6 each time the ‘n’ number is increased by 1.

The ‘T’ ...

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