# Maths help needed

Discussion in 'CycleChat Cafe' started by Milo, 26 Apr 2008.

1. ### MiloVeteran

Location:
Melksham, Wilts
Ok i have a number grid that is 10 across and ten down.
with numbers running from 1 to 100 or more.
A box is drawn on this grid and i need to find the product of the top left number and the bottem right number in this box.
I must do the same with the top right and bottem left numbers.
I then have to calculate the differnce between these two numbers.
I have to do this until i can find a formulea which i have maneged to do for the even boxes e.g 2x2 3x3 4x4.
The formulea I have found that works is the following 10 (n-1)2 (squared cant find chacter on keyboard)
Now my problem is when I try and find the formulea on the odd size grid boxes e.g 3x2, 4x3, 5x4
Anybody know of a forulea to work out what the next grid box differnce would be for example the differnce in a 7x7 grid is 300 what formulea would i use to find out the differnce in a 8x7 grid.
Any help would be most appreciated im rubbish at maths and this is driving me mental.

2. OP

### MiloVeteran

Location:
Melksham, Wilts
BUMP this is rather urgent BtW

3. ### zimzum42Legendary Member

This might sound like a silly suggestion, but why not go to a university website and look up the maths profs and send them an email or give them a call?

I've approached university staff, sometimes very eminent ones, to answer what to them must be simple questions, and they've always been great about it....

4. OP

### MiloVeteran

Location:
Melksham, Wilts
Its dead simple stuff only gcse but i cant get my head round it just hoping someone on here may know.

Location:
East London
6. ### killiekosmosÜber Member

Assuming you start at number N with a box X by Y. The corners are
Top left: N Top Right N + (X-1)
Bottom left: N + 10(Y-1), Bottom right N + 10(Y-1) + (X-1)
Top left * Bottom right is: NN + 10NY -11N + NX

Top right * Bottom left is: NN + 10NY-11N + NX + 10XY -10X - 10Y + 10

Difference is: 10XY -10X-10Y+10

= 10(XY-X-Y + 1) QED

Now can you come and do my garden?

7. ### marinyorkResting in suspended Animation

Location:
Logopolis
Where does the factor of 10 come in from, is it some different table from what I wrote down? I have the same formula without the 10.

Oh I see we've drawn different tables helps if one reads the original post sums and not products etc. If you do a multiplication table starting with n it gets even more different.

8. ### marinyorkResting in suspended Animation

Location:
Logopolis
Formula for miloats table is 10(XY-X-Y+1). Formula for sums table is XY-X-Y+1. Formula for multiplication style table difference of two products miloat style is (N-1)(N+(X-1))(N+(Y-1)). A fourth table has the rather boring 0 for miloat's table done with differences of sums, that one would have made an interesting piece of coursework! Can see why that was coursework the multiplication miloat table is slightly more complicated than the standard miloat one whilst not being as absurdly easy as difference of sums but similar to a multiplication table having sums differenced.

9. ### bonj2Guest

how do you know wh ich number is in which box miloat.
it runs from 1 to 100 OR MORE? how can it run to 100 OR MORE if there are only 100 boxes?
Draw it.
and what do you actually have to work out?
is it like sudoku?

10. ### marinyorkResting in suspended Animation

Location:
Logopolis
It could start 2 and so the 4 "corners" of the table would be 2,11, 92 and 101. The modular difference of this 1012-202=810. This corresponds to the formula 10(10x10-10-10+1)= 810. Whatever number you start with you get 810. As I have pointed out there are four sorts of tables and they all have difference formulas.

11. ### killiekosmosÜber Member

I've assumed it is a 10 by 10 grid with boxes numbered 1 to 100 in sequence. So going down any column values change in steps of 10.

12. OP

### MiloVeteran

Location:
Melksham, Wilts
Thats it exactly killkosmos just imagine a 10x10 grid going to 100 you draw a box on that grid and multiple the two diagonalizes then found out the difference.
I just cant find the formula to work out it out on the grids that are 4x3, 5x4 etc.

13. ### bonj2Guest

right, yeah. haven't fully read it but on the basis of my own maths expertise marinyork's response "looks right" so i'd go with that. Try and understand it, if you don't post why.

14. OP

### MiloVeteran

Location:
Melksham, Wilts
The formulea I have for for the 2x2 3x3 4x4 grids is 10 (n-1) cubed
NOw if someone could tell me the formula in those terms for the 3x2 4x3 5x3 grids in the same manner as I have the formula for the 2x2 grids I will be your eternal slave.
Im afraid some of the previous posts have snapped my tiny little mind.

15. ### bonj2Guest

so the grids always 'fit into' a 10x10 'super' grid, so a 'sub'-grid can never be more than 10x10, is that right?
So, within that 10x10 grid which is FIXED, there's 3 variables: (a) start number of 'sub'-grid, ( length of 'sub'-grid, (c) height of 'sub'-grid.
Still following?
And the result you want to arrive it is ALWAYS ((TLxBR) - (TRxBL))
(where T, L, B, R are top, left, bottom right of 'sub'-grid). right?

just trying to understand the situation.