Logical Consistency

In logical consistency questions, you are given a main statement followed by four statements. You would have to pick a combination of two of these four statements, which are logically correct and are consistent with the main statement given. Consider the following example:


R is in the room when P is in the hotel.


Can R be in the room when P is not in the hotel?


YES


The condition given in the first statement is that if P is in the hotel then R definitely has to be in the room.


R can be in the room otherwise also i.e. when P is not in the hotel.


The valid conclusions you can make about the main statement given are:
(a) P is in the hotel; R is in the room (straight logic)


(b) R is not in the room, P is not in the hotel (straight negation)


The statement above is also correct because, at any given point of time R and P have two possible positions each i.e. R can be in the room or outside.


P can be in the hotel or outside


When R is not in the room; P has two options, of either being in the hotel or outside. However it can be said definitely that P is not in the hotel because if P is in the hotel than R would be in the room, but R is outside, so P has to be outside. There are some standard types of questions in this category.


I.   If type


II. Either – or type


III.    Whenever – type


IV. May-be type


A simple logical can be followed in all these questions. Every main statement will have two parts X and Y. For example in the statement


R is in the room, when P is in the hotel.


X is ‘P is in the hotel’.


Y is ‘R is in the room’.


If the condition is when X then Y the valid conclusion would be when not Y then not x.
If X happens then Y will Happen


Now if Y happened it does not necessarily mean that X has also happened. Keep this point in mind and the exercises will be easy.