## Very Hard problem

Advanced methods and approaches for solving Sudoku puzzles

### Very Hard problem

I am still trying to complete my first Very Hard puzzle. Could anyone suggest where I can go from here?

**3 4** *7*
1** *7* 3**
987 312 546

**8 6** *5*
*3* *** 61*
*** **5 4**

*** 82* *64
**2 *9* **5
*7* **4 9**

Help!
Guest

Look at box 9 and focus on the number 7.

Then remove the number 7 from the list of candidates in a cell in box 6. Now there is one cell which only has one candidate...
Animator

Posts: 469
Joined: 08 April 2005

If you are still stuck after that:

* Look at box 8, concentrate at the number 5, now look at row 9
* Look at box 5, focus on the numbers: 3, 4 and 8
* now take a new look at column 5, and combine that with the possibilities for 3, 4, and 8 in box 5. (you can exclude 3, 4 and 8 from several cells in column 5)
* take a look at row 9, look closely at the numbers 1, 5, 6
* now look at column 9. if you've done the previous steps correctly then you should be able to fill in a number...
Animator

Posts: 469
Joined: 08 April 2005

Ok....

1. Box 8 5 must be r9 c 4 or 5
2. 3,4 and 8 must occupy column 5 in box 5
3. therefore r1 c5 and r9 c5 must have 5,6.
4. don't see anything special about number 1...
5. still cannot place anything in c9
Guest

Posts: 312
Joined: 25 November 2005

Possibilities of row9:

r9c1: 3, 5, 6, 8
r9c3: 1, 5, 6
r9c4: 1, 5
r9c5: 5, 6
r9c8: 2, 3, 8
r9c9: 1, 2, 3, 8

Look closely at r9c3, r9c4 and r9c5. If you still don't see it then try to fill in the number 1, 5 and/or 6 in any other cell then those three...
Animator

Posts: 469
Joined: 08 April 2005

So, r9c3, r9c4 and r9c5 can only have the numbers 1,5,6. ..

So, r7c7 or r8c7 must contain 1. therefore r1c9 must contain 1 !

Thanks !!
Guest