Aptitude - Permutation and Combination - Discussion

You can do either of the way either consonants first or the vowels first.

Just separate the Word CORPORATION along with the vowels i.e

CRPRTN: These are 6 consonants, as are is repeated two times you need to divide it by 2!

Hence, 6+1 = 7!/2! = 5040/2 = 2520.

1 was from the set of vowels.

(OOAIO) - These are 5 vowels which is represented as 1 set.

Now, from the Vowels we get.

5!/3! = 120/6 = 20.

i.e 2520*20 = 50400.

Given a set [ABCDEFGHIJKLMNOPQW]. In how many ways can we form a non repeated sub-set of 4-letter with letters (AB) being constant in every sub-set. Example [ABCE], [ABDC].

Find the number of ways in which an arrangement of four letter can be made from the letters of PRECIPITATION?

Please help me to solve this problem.

What is the difference between permutation and combination? I seriously can't understand the logic.

Is there someone who can help me out to understand the difference between both of them.

Where in question 3 does it indicate that only one vowel and only one consonant from the alphabet are permitted? Since this question appears to duplicate the wording of question 2, why isn't it solved in a like manner ? What am I missing here ?

How come 7!/2! Is 2520? 7!/2! = (7*8) / (2*1) = 32 isn't? Then how 2520?

@Aarthi,

The combination is selection only whereas permutation is selection + arrangement.

For example:

A committee should be formed with 2 persons from A, B, C, therefore, the should be {AB, BC, CA} only not {AB, BC, CA, BA, BC, CA} because AB and BA both are the same combination.

Next, If the question is like committee should be formed with one president and one vice president the answer is {AB, BC, CA, BA, BC, CA} because, in the combination AB, A can be president and B can be vice president and vice versa. So both are different.

The give word consistent of 5 vowels and remaining 6 letters + 1 group of vowels is 7!. So to get answer we must do 5! * 7!.

Is this correct? I am getting wrong answer.

Please Help me.

But here, R is repeated 2times, in vowels O is repeated 3 times. So we have to consider R & O.

So, 7!/2! & 5!/3! is taken.