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Approaching a Problem

Mostly the questions asked in the CAT are self-explanatory, i.e., they clearly mention what process is to be used—permutation or combination.

In case, the question does not specify this, you should try to find out whether it is a case of permutation or a case of combination. Sometimes the problem very clearly states whether it is the number of permutations (or arrangements) or the number of combinations (or selections) that has to be found out. The questions can be as follows:
For permutations:

“What is the number of permutations that can be done…” or “What is the number of arrangements that can be made…” or “Find the different numbers of ways in which something can be arranged…etc.

For combinations:
“What is the number of combinations that can be done…” or “What is the number of selections that can be made…” or “Find the different numbers of ways in which things can be selected etc.

Some other standard examples of permutation and combination are:
Permutation Word formation, number formation and circular permutation etc.
Combination Selection of a team, forming geometrical figures, distribution of things (except some particular cases).
Still, sometimes the questions may not explicitly state what you have to find—permutation or combination. In that case, the nature of what is to be found out will decide whether it is the number of permutations or the number of combinations.
See the example given below
I have to invite two of my eight friends to my anniversary party. In how many different ways can I do this?
Assume my eight friends are A, B, C, D, E, F, G and H. Whether the two friends that I call for the party are A and B or B and A, does not make any difference. As we have discussed before, that what matters most in case of permutation is the order of occurrence of things. As order does not play any role here, it is clearly the case of combination.

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