Tips and Tricks on Logical Deductions


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

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.

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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