The New Sudoku Players' Forum

[The Jackle]

- - - - - - - - -
l 0 0 0 0 0 0 2 4 0 l Hi well im in year 7 and have absolutely no idea
l 9 7 2 0 0 0 0 0 0 l
l 0 0 4 0 0 6 0 1 0 l How to do Sudoku. (Its Maths Homework). And i
l 7 0 6 2 0 5 0 0 0 l
l 8 4 0 0 1 0 0 3 2 l Was wondering if you could explain how to
l 0 0 0 3 0 9 7 0 4 l
l 0 9 0 4 0 0 6 2 0 l Actually work it out and help me through thisone.
l 4 0 0 0 0 0 1 7 3 l
l 0 2 1 0 0 0 0 0 0 l Thanks. ( This is the problem on the left ).
- - - - - - - - -

-The Jackle

[Cec]

Hi The "Jackle",

In a sudoku puzzle each row, column and box must contain all of the numbers from 1 to 9.

Click on the following link for an explanation of the rules of a sudoku puzzle and how to solve them :

http://www.paulspages.co.uk/sudoku/howtosolve/index.htm

Your puzzle looks like this:

Code: Select all

 *-----------*
 |...|...|24.|
 |972|...|...|
 |..4|..6|.1.|
 |---+---+---|
 |7.6|2.5|...|
 |84.|.1.|.32|
 |...|3.9|7.4|
 |---+---+---|
 |.9.|4..|62.|
 |4..|...|173|
 |.21|...|...|
 *-----------*


Note that the puzzle grid comprises nine 3X3 "Boxes". The top left Box is Box1 (contains digits 9,7,2 and 4), the top right Box is Box3, the middle Box is Box5 and the lower right Box is Box9 etc. Because both Boxes 5 and 9 already contain five "given" digits then look at these Boxes first.

In Box 5 the missing digits are 4,6,7 and 8. Because digits 1 to 9 can only appear once in every row, column and Box of a sudoku puzzle, then there is only one cell in Box5 for placing a 4. This now leaves only one cell in Box 5 for placing an 8, then only one cell for placing a 6 in this Box and one cell left to place the 7 in this Box5. This completes solving Box5.

Now try placing the four required digits 4,5,8 and 9 to fill the four blank cells in Box9 using similar "dicing" of rows and columns as used above.

Hope this enables you to solve the rest of this puzzle.

Cec

[The Jackle]

Thanks Cec for replying. I think i understand now.
This is the completed version.

*-----------*
|153|897|24.6| Complete
|972|154|385| Can you tell me if this is wrong or right? And if wrong
|684|326|917| where did i go wrong?
|---+---+---|
|736|245|891|
|849|716|532|
|215|389|764|
|---+---+---|
|597|431|628|
|468|962|173|
|321|578|459|
*-----------*

Thanks.

[HATMAN]

Yes you've gone wrong you have a few duplicates, your blocks are correct but:
R2 2*5
R3 2*6
R8 2*6
R9 2*5
C4 2*3
C6 2*6
The correct solution is:
+-------+-------+-------+
| 1 6 3 | 5 9 8 | 2 4 7 |
| 9 7 2 | 1 3 4 | 8 5 6 |
| 5 8 4 | 7 2 6 | 3 1 9 |
+-------+-------+-------+
| 7 3 6 | 2 4 5 | 9 8 1 |
| 8 4 9 | 6 1 7 | 5 3 2 |
| 2 1 5 | 3 8 9 | 7 6 4 |
+-------+-------+-------+
| 3 9 7 | 4 5 1 | 6 2 8 |
| 4 5 8 | 9 6 2 | 1 7 3 |
| 6 2 1 | 8 7 3 | 4 9 5 |
+-------+-------+-------+

[Cec]

"Can you tell me if this is wrong or right? And if wrong where did i go wrong?.."

Sorry Jackle but your answer is wrong. Although it is mentioned in the above link, I should have emphasized that the numbers 1 to 9 can only
appear once in any row, column or box.

Your "solution" is incorrect because it shows:

two 5's in row 2
two 6's in row 3
two 6's in row 8
two 5's in row 9
two 3's in column 4
two 6's in column 6

Whilst you have the correct numbers in Box4 I suggest you start from scratch again.

When placing a number and again suggesting you start with Box 5, make sure the number you place does not already exist in the same row or
column. To better illustrate this, you incorrectly placed the 6 in cell r5c6 but overlooked that a 6 already existed in the same column 6. The correct placement for the 6 was in cell r5c4 because there was no 6 in column 4 or row 5. A 7 would then fill the remaining cell r5c6 in Box 5 and you should do a final check that there are no other 7's either in column 6 or row 5.

I emphasize the need to make haste slowly and particularly to check both the corresponding row and column relating to the particular cell you place a number in. Good luck but it looks like some more homework Jackle

PS. I've noticed HATMAN has replied but decided to let my post stay to help (I hope) Jackle know where he went wrong.

Cec

[HATMAN]

Cec

You're right to do so - I should have been more positive but I was short of time.

Maurice

[Cec]

Thanks Maurice... No cricket or good movies on telly last night so I had the time

Cec

[The Jackle]

Mmm ok.

I have maths tommorrow

And i'll get a new puzzle to do.

Thanks for the help guys.

[Pat]

each row, column and box must contain all of the numbers from 1 to 9

yes, exactly,

Fill the grid so that
every column, every row and every 3x3 box contains the digits 1 to 9

the numbers 1 to 9 can only appear once in any row, column or box.

Your "solution" is incorrect because it shows:

two 5's in row 2
two 6's in row 3
two 6's in row 8
two 5's in row 9
two 3's in column 4
two 6's in column 6

the rule is silent on duplicates.

( of course if you wish, we can easily prove the theorem. )

i'd describe the error as

row 2 is missing the 6
row 3 is missing the 5
etc

[Cec]

"...the rule..."

I was unaware of any definite "rule" which had to be rigidly adhered to when explaining the "rules" of solving sudoku. Here's some "rules" I've noted in Forum posts.

"Each row, column and box must end up containing all of the numbers from 1 to 9."

"The One Rule:
Fill in all blank cells making sure that each row, column and 3 by 3 box contains the numbers 1 to 9.

"....Each unit must contain the digits 1 through 9...."

"each row, column and box must contain all of the numbers from 1 to 9

Fill the grid so that every column, every row and every 3x3 box contains the digits 1 to 9

In my opinion, each of the above five "rules" provides the same explanation as to how to complete a sudoku grid.

"the rule is silent on duplicates"

Yes, OK. but members seem to prefer mentioning duplicate numbers for pointing out incorrectly posted puzzles such as HATMAN above .

Cec

[stumble]

I'm kind of interested in why a math teacher would incorporate Sudoku into the lesson plan. Sudoku does teach reasoning, but it seems like most math regimes employ reasoning, and it would be make more sense to teach reasoning using standard math protocols: algebra, say. Of course if the teacher is going to dissect Sudokus with standard math, I wanna audit the class!

[Pat]

...the rule...

I was unaware of any definite "rule" which had to be rigidly adhered to when explaining the "rules" of solving sudoku.

Here's some "rules" I've noted --

Each row, column and box must end up containing all of the numbers from 1 to 9.

The One Rule:
Fill in all blank cells making sure that each row, column and 3 by 3 box contains the numbers 1 to 9.

Each unit must contain the digits 1 through 9

each row, column and box must contain all of the numbers from 1 to 9

Fill the grid so that
every column, every row and every 3x3 box contains the digits 1 to 9

In my opinion, each of the above five "rules" provides the same explanation as to how to complete a sudoku grid.

hey Cec, thanks for collecting all those quotes

myself, i already knew the rule

but the extra quotes may help convince anyone else who may have some doubt

[Pat]

the rule is silent on duplicates

Yes, OK. but members seem to prefer mentioning duplicate numbers for pointing out incorrectly posted puzzles such as HATMAN above .

yes, so far it is sadly 2-to-1 against me

[Cec]

"...hey Cec, thanks for collecting all those quotes

myself, i already knew the rule

but the extra quotes may help convince anyone else who may have some doubt

Pat, I have a confession to make. I previously thought you were being "petty" but it's only just dawned on me that you were quoting the "rules' of sudoku whereas I quoted how a correctly completed sudoku puzzle should look.. Just as well I didn't post my first draft reply to you tonight .

the rule is silent on duplicates

Yes, OK. but members seem to prefer mentioning duplicate numbers for pointing out incorrectly posted puzzles such as HATMAN above .

yes, so far it is sadly 2-to-1 against me

I'm even unsure how to interpret your meaning here... Is it "tongue-in-cheek"? My comment was of course not based specifically on this puzzle but on my recollection in general as to how members usually explain incorrectly posted puzzles by referring to duplicate numbers in rows or columns rather than a missing digit.

Cec

[Pat]

yes, so far it is sadly 2-to-1 against me

I'm even unsure how to interpret your meaning here... Is it "tongue-in-cheek"?

My comment was of course not based specifically on this puzzle but on my recollection in general as to how members usually explain incorrectly posted puzzles by referring to duplicate numbers in rows or columns rather than a missing digit.

most serious

definitely not t-i-c

i may be in the minority -- not the first time! -- and this saddens me