Logical Consistency

Logical Consistency questions have a main statement followed by four answer alternatives. One of these is logically correct and consistent with the main statement. Again, speed is a crucial factor here.
For example,
Main Statement: If you are in the IIMs, you have cleared the CAT.

It is very evident that if I am in the IIMs, I have cleared CAT. Can we also conclude that if I am not in the IIMs, I have not cleared CAT? No. Is it possible for one to have cleared CAT and not be in the IIMs – YES. The statement says that if you are in the IIMs, you have definitely cleared the CAT. But one can clear CAT and choose not to be in the IIMs.

Thus the only conclusions possible are:
1. you are in the IIMs implies you have cleared CAT.
2. you have not cleared CAT implies you are not in the IIMs.

The main statement may have any of the following variants:
1. if
2. if and only if
3. whenever
4. either….or
5. only when
Let us understand the difference between the “if” and “if and only if” as well as the “when” and “only when” type of questions.

Statement : If it rains, the ground is wet.
Meaning : Here the ground can be wet otherwise also, i.e. when it does not rain. But if it rains the ground is surely wet.

Statement : If and only if it rains, the ground is wet.
Meaning : Here the ground cannot be wet otherwise i.e. if the ground is wet, it must have rained. Also, it goes without saying that if it rained, the ground is wet.

Statement : When Raj studies, he gets a headache.
Meaning : Here he can get a headache otherwise also.

Statement : Only when Raj studies, he gets a headache.
Meaning : Here Raj cannot get a headache due to any reason other than studying.

The “either-or” type of question is as simple as the name suggests – either this or that e.g.

Statement : Either Sushmita or Aishwarya is beautiful
Here the conclusions can be:
1. Sushmita is beautiful implies Aishwarya is not beautiful
2. Aishwarya is beautiful implies Sushmita is not beautiful

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