Monday 22 February 2016

Syllogism Short method

Today I am going to share systematic method to solve Syllogism questions. In every competitive exam, you will see at least 4-5 questions from this chapter.

I will start with explaining basic syllogism terminology which will be followed by practical examples.
 
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    All






    Some




    NO



    Case #   All - Some






    Let! 

               You have 1000 $ in your pocket.One of your friend needs 600 $ to pay his Bill.He wants to borrows money from you.He comes to you and say,"Do you have 600 $ ?.What would you say,"Afcoss Yes!".Even if He ask for 1 $, or 999 $ .Your answer will always "Yes!". 

    So Overall you had 1000 $ which is called "All " or All of the money you had & What is your friend want some of the money like here 600 or it could be 1$ or 999 $ and what we call that some portion of money out of it.or " Some".

     That's why In " All " Case, "Some" is always true.



    Example: 



    Statement : All A are B.

    Possible Diagram


    Conclusion

    All A are B             

    Some A are B         

    Some B are A         

    Some A are not B     

    Some B are not A   ✘ 





    Now Here we can see that A contains set of numbers. So we call it is as Set A and Same for B 'Set B'.


    All the numbers in A is contains by B hence All A is B true But All the numbers in B is not in A or not contain by A so All B is A → False.



    Now Let understand How All A is B → True But All B is A  False

    Let  Box A & Box B . Here We can see that Box B is inside the Box A Hence Box B can fit into Box A but Box A cannot fit into Box B.




    Case #    Some - Some Not


    Assume you have given the exam & you passed with some marks that means you got some marks and some or not.even if you passed the exam with 99% marks still you missed the 1%. So Even 99% is count under the some case.and 1% is also count under some case.hence In 'Some' case 'Some Not' is true.


    Statement : Some A are B

    Possible Diagram



    Conclusion


    All B are A        

    Some B are A    
    No A is B          


    Statement : Some A are not B
    Possible Diagram





    Explanation








    Here we see that Set A & Set B has some common values hence we can say that Some A is B & Some B is A But there also some values which are not common in both A & B.So We can also say that Some A are not B & Some B are not A.

    Case #    No- Some Not

     
    Assume You have no money in your pocket.So if you got no money.It means also that some money is not in your pocket.Having No means also some not.

    Point to Remember while Solving Syllogism

    • Anything is possible in a statement.                                                                                                        like  Some pens are fans. No fan is heater
    • Negative Answer will never be there.

    Simple Case

    Statement Conclusion
    Some All , No ,  [ False ]
    Some,Some Not [ True ]
    All No , Some Not [ False ]
    Some , All [ True ]
    Some Not Only Statement [ True ]
    No Some , All [ False ]
    No , Some Not [ True ]


    Possibility
    Statement Conclusion
    Some No , Some [ False ]
    All , Some Not [ True ]
    All
    No
    Some Not Some Not , All [ False ]
    Some , No [ True ]

    Some Examples


    Statement : Some A are B, Some B are C , All C are D


    Conclusion

    Some A are not D ✘

    Some B are D       

    Some A are C       ✘


    Statement Some A are B, Some B are C, No C is D


    Conclusion

    Some B are not D  ✘
    Some D are not B  ✘  

    Some A are C        ✘


    Statement All A are B , All A are C , All A are D , No D is E


    Conclusion

    Some B are not E 

    Some A are not E 

    No C is E              

    No A is E             

    No E is A             


    Statement : Some A are B, Some B are C, Some C are D, Some D are E



    Conclusion

    Some C are not A  ✘

    Some B are not D  ✘

    Some A are E        ✘

    All B are D            ✘

    No A is E               ✘

    Some C are A        ✘

    All B are E            ✘

    No B is E              ✘


    ' Either Or ' & ' Neither Nor '


    Complementary Pair


              1. If One Conclusion is positive & One is Negative

                

                No - Some

                Some - Some Not

                All - Some Not

           

           2.  Same Subject & Same Predicate are there
           3.  & not able to draw both the conclusion then answer will be Either Or


    Example

    Statement All A are B , All A are C , All A are D , No D is E, Some F is C




    Conclusion




    Statement : Some A are B, Some B are C, Some C are D, Some D are E
    Conclusion


    Exception

    1. In case of Universal (like 'All & No' ) Conclusion Complementary pair does not work

    2. In this type of Question " Neither Nor "


    Statement Some A are B, All B are C, No C is D


    Conclusion

            Some A are not D    ✘    

            No B is D                ✘

            Some A are C           ✘

            Some D are B           ✘


    Statement All A are B, No B is C , All C are D


    Conclusion 

    Some A are not D ✘

         No D is B             ✘

         No A is C             
       No A is D            
       No D is A            ✘



    Possibility:

    Statement Some A are B, Some B are C



    Conclusion






    Explanation (Simple case A,B & C) :



     Let A, B & C are three person. A & B knows each other. B & C knows each other But B knows both.Now Will A talk about C ? Answer is 'Not!,Neither Positive Nor Negative' because he doesn't knows him.So conclusion C is False.



    Possibility Case (Conclusion : D,E & F) :



    Now Lets take a look at conclusion E.Now Suppose there is raining outside your home and someone comes to you and say there is a possibility to rain today.What would you say to him,'Mad!"Same scenario is here By looking at diagram it clearly says that Some B are A then how could be say it is 'possible' which is actual there.Hence Possibility make it wrong or false the conclusion.So Conclusion E is wrong.



    Now talk about conclusion F which says Some A are not c which we don't know but it says let it is a 'possibility' so anything could be possible which doesn't make our statement wrong or contradict with statement.If we make it like this below:


    We talk here about possibility which could be anything which especially not contradict with our statement.So F which was False in Simple Case but When we talk about possibility is became true.

    Let another example for this.Now Let There is a cloudy sky outside your home.Someone comes to you and say ," There is a possibility that there might be rain today",Now you have no idea whether it rain today or not.So you might be say ," Bro! It is possible".Now here you cannot talk about negative because in Syllogism Negative Answer will never be there.


    In a statement word like these called possibility
    • Can be 
    • Possible
    • May be / might be
    • Chances
    • Occurs
    • is being possibility
    • is a possible
    In a statement word like these called surety
    • Can Never be
    • Can

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