Number Grid

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Number Grid

Introduction

I am going to be looking at a 10x10 square and drawing a square around a 2x2 square around 4 numbers and multiplying the top left number by the bottom right number and multiplying the top right number by the bottom left. I will find out the difference and do 2 more and see if there is a pattern. I will then investigate this further. I will first be looking at a 10x10 square.

2x2

Example 1

Top Left x Bottom Right-12 x 23= 276

Top Right x Bottom Left-13 x 22= 286

286-276=10

The difference is 10. I will now look at 2 more examples and see if this continues

Example 2

                    Top Left x Bottom Right-35 x 46= 1610

                          Top Right x Bottom Left- 36 x 45= 1620

   

                           1620-1610=10

Example 3

                        Top Left x Bottom Right- 81 x 92=7452

                        Top Right x Bottom Left- 82 x 91=7462

                     

   

                        7462-7452= 10

The difference of all 3 examples was 10 so it must be the same for any 2 x 2 in that particular number grid.

General Rule For 2x2

If we look at the 2x2 algebraically then it would look like this:-

                             Top Left x Bottom Right- (X)(X+11)=X2+11X

                             Top Right x Bottom Left- (X+1)(X+10)=X2+11X+10

Prove

X=2

Top Left x Bottom Right-(2)2+11(2)=4+22=26

Top Right x Bottom Left-(2)2+11(2)+10=4+22+10=36

36-26=10    QED

This proves the difference is always 10

3x3

I will now be looking at a 3x3 square and seeing if it follows a rule as well.

Example 1

                                          Top Left x Bottom Right- 36 x 58= 2088

                                          Top Right x Bottom Left- 38 x 56= 2128

                                           2128-2088= 40

The difference is 40. I will now do 2 further examples to see if this is the same for those 2

Example 2

                              Top Left x Bottom Right- 72 x 94= 6768

                              Top Right x Bottom Left- 74 x 92= 6808

                              6808-6768= 40

Example 3

 

                           Top Left x Bottom Right- 6 x 28= 168

                           Top Right x Bottom Left- 8 x 26= 208

                           208-168

General Rule For 3x3

If we look at the 3x3 square algebraically it would look like this:-

                                     Top Left x Bottom Right- (X)(X+22)=X2+22X

                                     Top Right x Bottom Left- (X+2)(X+20)=X2+22X+40

Prove

X=2

Top Left x Bottom Right- (2)2+22(2)=4+44=48

Top Right x Bottom Left- (2)2+22(2)+40=2+44+40=88

88-48=40    QED

This proves the difference is always 40

4x4

I will now be looking at a 4x4 square to see if it follows a pattern

Example 1

                                                                 

                                                             Top Left x Bottom Right- 32 x 65= 2080

                                                             Top Right x Bottom Left- 35 x 62= 2170

                                                             2170-2080=90

The difference is 90. I will now do 2 further examples to see if this the same for those 2

Example 2

                                                                   

                                                       Top Left x Bottom Right- 67 x 100= 6700

                                                       Top Right x Bottom Left- 70 x 97= 6790

                                                        6790-6700=90

Example 3

                                                        Top Left x Bottom Right- 1 x 34= 34

                                                        Top Right x Bottom Left- 4 x 31= 124

                                                        124-30= 90

General Rule For 4x4

If we look at the 4x4 square algebraically it would look like this:-

   

                                                   Top Left x Bottom Right- (X)(X+33)=X2+33X

                                                   Top Right x Bottom Left- (X+3)(X+30)=X2+33X+90

Prove

X=2

Top Left x Bottom Right- (2) 2+33(2)= 4+66= 70

Top Right x Bottom Left- (2) 2+33(2)+90=4+66+90=160

160-70= 90  QED

This proves the difference is always 90

                                                                                                                         General Rule For A N x N Square

An N x N square can also be written like this. I have only included the four numbers that are used in the multiplication as the others are not necessary in this equation.

                                                             

Top Left x Bottom Right- (X)(X+10(N-1)+(N-1))= X2+10X(N-1)+X(N-1)

Top Right x Bottom Left- (X+(N-1))(X+10(N-1))= X2+10X(N-1)+X(N-1)+10(N-1)2

T.R. x B.L. – T.L. x B.R.= X2+10X(N-1) X(N-1)+10(N-1)2-X2+10X(N-1)+X(N-1)

                                        = 10(N-1)2

Prove

 N=2

10(N-1)2= 10(2-1)2= 10(1)2=10(1)=10 QED

*the difference for a 2x2 square is 10

This shows that the formula 10(N-1)2 can be used to work out the difference of any N x N square

I will now be looking at the different rectangular formations in this 10x10 number grid and seeing whether they follow any patterns.

3x2

I will now be looking at a 3x2 rectangle and seeing if it follows a pattern

Example 1

                                Top Left x Bottom Right- 3 x 15= 45

                                Top Right x Bottom Left- 5 x 13= 65

                                65-45=20

The difference is 20. I will now do 2 more examples and see if it is the same for those 2 as well.

Example 2

                                 

                                   Top Left x Bottom Right- 28 x 40= 1120

                                   Top Right x Bottom Left- 30 x 38= 1140

Join now!

                                    1140-1120=20

Example 3

                                  Top Left x Bottom Right- 74 x 86= 6364

                                  Top Right x Bottom Left- 76 x 84= 6384

                                   6384-6364=20

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