T - Total. Looking at the 9-9 grid below and the T-shape drawn on it, The total number of the numbers on the inside of the T-shape is called the T-total

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Mathematics GCSE                              T – Total                                James De Souza

Investigation into T shapes

Looking at the 9-9 grid below and the T-shape drawn on it,

The total number of the numbers on the inside of the T-shape is called the T-total

1    2   3   4   5   6   7   8   9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

37 38 39 40 41 42 43 44 45

46 47 48 49 50 51 52 53 54

55 56 57 58 59 60 61 62 63

64 65 66 67 68 69 70 71 72

73 74 75 76 77 78 79 80 81

82 83 84 85 86 87 88 89 90

The t-total for this T-shape is:

1+2+3+11+20=37

So 37 = T-total

The number at the bottom is the T-number, so the T-number for this shape is 20 

Aims:

1) Investigate the relationship between the T-total and the T-number

2) Use the grids of different sizes. Translate the T-shape to different positions. Investigate relationships between the T-total, the T-numbers and the grid size.

3) Use grids of different sizes again. Try other transformations and combinations of transformations. Investigate relationships between the T-total, the T-numbers and the grid size and the transformations.

Aim 1- the solution

1    2   3   4   5   6   7   8   9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

37 38 39 40 41 42 43 44 45

46 47 48 49 50 51 52 53 54

55 56 57 58 59 60 61 62 63

64 65 66 67 68 69 70 71 72

73 74 75 76 77 78 79 80 81

T22=3+4+5+13+22

=47

T69= 50+51+52+60+69

=282 

In the diagram below it shows the difference between the T-number and the other numbers. First is the T-shape in question:

1 2 3

  11

  20

This is the T-shape and here is the Difference T-shape:

N-19 N-18 N-17

          N-9

           N

This shows the difference N= T-number

Simplified this can be written as 5N - 63

In the T on the previous page I have noticed that the first difference from N is 19, which is also the width of the square multiplied by two plus one.

I’ll put that idea into another T. Note W= width number (9)

N-(2W+1)  N-2W  N-(2W-1)

Join now!

                   N-W

                     N

This is the same thing as before but shown algebraically.

The formula for the Value of the T-total now is shown as:

5N-7W=T-total

To prove that this works, take any number, for example t – number = 47.                                              

5 * 47 = 235. 235 – 7 * 9 = 63

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