solving syllogism questions by making venn diagram

solving syllogism questions by making venn diagram is the best and most accurate technique. Their r certain formulaes but u cannot rely upon them as they fail in many cases.

whenever we r given a statement try to make diagrams. Their can be many diagrams for a single statement. And most important fact is that in all the diagrams the statement should hold true.

Like if we have a statement : some A are B.

Now for this statement we can make 4 diagrams.

1. A diagram in which all A are inside B.

2. A diagram in which all B are inside A.

3. Some portion of A and B coincide.

4. Both A and B completely overlap each other. That means A=B.

Now in all these diagrams u will see that the statement is true. Since their r some A which r B in every diagram.

Now if we have a conclusion then we should check whether that conclusion holds true in all these diagrams or not. If it holds true then the conclusion is true, if even in a single diagram its not true then its false.

For example we take a conclusion : some B are A.

Here in all the diagrams this conclusion is true so we say that its true. Another example conclusion : some A are not B.

Now this conclusion is true in diagrams 2 and 3 discussed above but it fails in diagram 1 and 4. So we will say that this conclusion is false. 
for the statement : some A are not B.
For this statement we can make 3 diagrams.
1. A diagram in which all B are inside A.
2. Some portion of A and B coincide.
3. No portion of A is common with B.
In all the above diagrams the statement some A are not B holds True.
If we have a conclusion: some B are not A.
Now this conclusion hold true in diagram 2 and 3. Whearas in diagram 1 it is false. So we will say that this conclusion is false.  
for questions related to possibilities.
Whenever their is a conclusion based on possibilities, then we check whether that conclusion holds true in any of the diagram. If, its true even in a single diagram then the conclusion will be true.
For example statement : all A are B.
Conclusion 1: some B are not A.
Conclusion 2: it is possible that some B are not A.
Now for the statement we can make two diagrams.
1. All A are inside B.
2. A and B completely overlap each other.
Now the statement all A are B holds true in both the diagrams.
Now, the conclusion 1 is correct in diagram 1 but it is false in diagram 2. So the conclusion 1 will be false.
Conclusion 2 is also correct in diagram 1 but not in diagram 2. But since their is possible word in the conclusion so if, the conclusion satisfies any 1 diagram then it will be true. Hence conclusion 2 is true.

prepared by:- CHETAN DHAWAN