For those who missed the Sudoku GP Round-2 last weekend, it might be useful to try out some of the variants. Though, not explicitly mentioned, many of them turned out to be 'Converse'-like variants. Good practise before the Converse round in SM.
http://gp.worldpuzzle.org/content/sudoku-gp

A partcipant asked this question. Sharing it here as it may be relevant for all.


Since there is no X to the left of the first row, by converse rule, the sum of the first three numbers cannot be equal to X. (X=7 here) If row 1 column 2 has a 4 the sum of first three numbers in row 1 becomes 7. So this cell must contain 3.

Here are some of the practice puzzles for the three variations appearing in this test
Average Sudoku: http://www.funwithpuzzles.com/2015/11/average-sudoku-puzzles.html
Consecutive Sudoku: http://www.funwithpuzzles.com/2015/06/non-consecutive-sudoku-puzzle...
Kropki Sudoku: http://www.funwithpuzzles.com/2015/09/kropki-puzzles.html

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	Classic Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Many puzzles were worth too much or too little

Anybody give some clues on kropki sudoku 9*9 from IB. I want to know how to start as there are very few clues and I don't know where to start.

And also please give some starting clues for x sum frame 9*9 from IB.

Edited by shera90 2016-02-12 8:14 AM

Look at column 4. Because of the 2s in col5 and col6, a 2 must come in C4R1 or C4R2 -> this means C4R1 and C4R2 must have the numbers 2 and 3. Then C4R4 has possible options as 5,6,7. 5 and 7 are not possible because of converse rule. So it must have the number 6. C4R6 now has possible options 5 or 7. If it is 7 then C4R8 and C4R9 will be 4 and 5, which is not possible. So C4R6 must be 5. Now C4R9 must be 4 as we have a black circle. And C4R7 is 7.

In general, try to start around black circles, as they are the most likely places to start. Then try to look for long consecutive sequences in a row/column/box. If you are stuck or there is less progress initially, some amount of pencilmarking around the marked circles can help get the breakthrough. After that make sure you do not forget classic rules AND converse rules. For example, if a cell has 3 and there are no circles then the neighbours cannot be 2,4, or 6.

I hope you will be able to solve this one now.

>>>And also please give some starting clues for x sum frame 9*9 from IB.

IB X sum frame 9x9: C4R4 = 4 (singlet). Concentrate on C5... C5R4 and C5R6 must contain (2,6). So, R5C4 and R5C6 must contain (3,8). Also observe that, C3R4 = C7R6 = 8.

Can you explain how you got (2,6) and (3,8) ?

>>>And also please give some starting clues for x sum frame 9*9 from IB.

The starting approach has to be to find the possibilities for X, without forgetting classic rules.

For example, in the IB, if we look at column 6, the first three numbers can have three numbers from 3,5,8 and 9. So the possible values of X are 16, 17, 20 or 22.

Now look at row 6. The possible values for first three numbers are 2,6,7,8 and 9. Using these numbers, we cannot make 20. So X cannot be 20. Also, if X=16, then we need to have 2,6 and 8 as first three numbers. Then we cannot place any number in R6C5. So X cannot be 16 either.

The possible values for X are now 17 or 22.

Similarly, you can deduct that X cannot be 17 as it leads to a contradiction in Boxes 4/5/6.

Once X is identified as 22, there are only two ways to make 22 (589 or 679). You will be able to solve easily after that.

>>>Can you explain how you got (2,6) and (3,8) ?

In column C5, the middle 3 numbers (in r4,r5,r6) must add up to 12. Two numbers are 4 and 2, so 3rd one must be 6.
Why the middle numbers add to 12? Because in C5, 1st 3 numbers (r1,r2,r3) = (45 - X - 12), and last 3 numbers (r7,r8,r9) = X. So middle 3 numbers = (45 - (45 - X - 12) - X) = 12.

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Many puzzles were worth too much or too little

Really nice sudokus!
I was lost on both the Average sudokus... but otherwise it went smooth.
QuadMax 9x9 and X-Frame 9x9 were my favourites.

Thanks Harmeet and Rakesh.

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Fairly Nice
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	were not represented well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Below Average
Which set of puzzles did you like the most?	Classic Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth too much or too little

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Fairly Nice
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Fairly Nice
Which set of puzzles did you like the most?	X Sum Frame Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Many puzzles were worth too much or too little

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	Consecutive Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	X Sum Frame Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Average
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Many puzzles were worth too much or too little

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	Consecutive Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	X Sum Frame Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	representation could have been better
What was your opinion of the distribution of easy/hard puzzles?	Too many hard puzzles
What did you think about the puzzle quality of the test?	Fairly Nice
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth too much or too little

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Below Average
Which set of puzzles did you like the most?	QuadMax 4Odd 4Even
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

How well did the variants represent the theme of the test ?	variations represented the theme well
What was your opinion of the distribution of easy/hard puzzles?	Just right
What did you think about the puzzle quality of the test?	Very nice
Which set of puzzles did you like the most?	X Sum Frame Sudoku
Of the puzzles you solved/attempted, how well did the point values reflect the difficulty?	Most puzzles were worth the right amount

Thanks for another great test Rakesh and Harmeet. All of the puzzles I solved were very nice, but my favorites were QuadMax 2 and X Sum Frame 2 (I really liked the deductions for X in this one).