Tips and Tricks on Logical Deductions


 


1
This means that A leads to B, but does not mean the reverse.i.e. If B happened, A must have happened. In such situations A is a sufficient condition for B but it is not a necessary condition
The situation is better understood with an example as follows
If I go to a movie, I enjoy myself
This would mean that if I have gone to the movie, I will definitely enjoy myself. However it does not mean that if I have enjoyed myself, I must have gone to the movie-there are so many ways of enjoying yourself



2
In this case A is a necessary and sufficient condition for occurrence of B. In this case there is reversibility of logic. i.e. If B has happened A must have happened
Another example
Only if Saurab plays the match, will he get a hundred.
If Saurab has got a hundred he must have played the match.



   3
One of the two has to happen. At the same time the two events are exclusive of one another. If one happens the other will not happen
Either he becomes a TV star or he becomes a movie star.
For better understanding some example are as follows.
(a) Shahrukh acts like a hero
(b) Shahrukh does not act like a villain
(c) Shahrukh acts like a villain
(d) Shahrukh does not act like a hero
(i) c, d only (ii) b, a only (iii)cd & ba (iv)None of these
This question is based on an either-or premise. Thus we can see that cd is correct. Since if he acts like a villain-(statement c) he will not act like hero (statement d)


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