Post the puzzle or solving technique that's causing you trouble and someone will help

have been trying for a week, no clue how to solve

|_ 5 _ |_ 3 _ |_ _ _|
|_ _ 1 |6 _ _ |9 _ 8|
|3 4 _ |7 _ 1 |_ _ _|
-----------------------
| _ _ _| _ _ 7|_ _ 5|
| _ 9 _| _ _ _|_ 8 _|
| 7 _ _| 2 _ _|_ _ _|
-----------------------
|_ _ _ | 3 _ 9|_ 6 1|
|6 _ 4 | _ _ 8|3 _ _|
| _ _ _| _ 6 _| _ 7_|

thank you.
prettyhomemaker

Posts: 1
Joined: 13 March 2006

Can you see the pairs in r59c4, r29c6, then r6c35 ?
ravel

Posts: 998
Joined: 21 February 2006

prettyhomemaker wrote:trying for a week, no clue how to solve

Look for easy-to-spot stuff like this:

There is a 3 in row 1. It is in box 2
There is a 3 in row 3. It is in box 1
Well, there has to be a 3 in row 2 in box 3.
But there is only one cell in row 2 box 3 that is empty
So that solves one cell!

Unfortunately, we just ran out of easy ones. The 7 in row 6, box 4 and row 4, box 5 look tempting. So we look at row 5 in box 6. Rats! There are two empty cells, so we don't know which to pick. Forget 7's for now. In fact, forget easy ones.

OK, tougher: Look at the cell at row 2, column 1 (r2c1). What could go there?
123456789, initially, but then we arrive at
-2---6789 because Box 1 already has 1345, right. Then
-2----7-- because row 2 already has 13689. Then finally
-2------- because column 3 already has 367
So only a 2 can go there. Another cell solved!

How did I happen to chose cell r2c1 to investigate? Well, it looked promising due to so many digits in row 2 and box 1.

So using that logic, lets look at row 2 col 2. Yep! It is 7 by the same logic used above.

OK, we have a 7 in column 1 and column 2. That means there has to be a 7 is column 3 and it has to be in box 7, namely either r7c3 or r9c3. Well, it looks like we're stuck again: Which one to choose? Luckily we see that there is already a 7 in row 9. That means our 7 HAS to go into r7c3. Another one solved.

Now see if you can figure out why the next 7 has to go into r8c5. Look up as well as to the right and left.

Oh, no! That only got us this far
Code: Select all
`-5-  -32  ---271  6--  93834-  7-1  ------  --7  --5-9-  ---  -8-7--  2--  -----7  3-9  -616-4  -78  3-----  -6-  -7-`

but we can't get further without more complicated techniques. I suggest throwing this puzzle into the back of your drawer and then getting some easy puzzles somewhere. When you can do easy puzzles in your sleep, dig this one out again. You are ready for "pencilmarks".

For my tutorial, see www.sudoku.funurl.com

Mac
QBasicMac

Posts: 441
Joined: 13 July 2005