Aptitude - Permutation and Combination - Discussion
Discussion Forum : Permutation and Combination - General Questions (Q.No. 12)
12.
How many 4-letter words with or without meaning, can be formed out of the letters of the word, 'LOGARITHMS', if repetition of letters is not allowed?
Answer: Option
Explanation:
'LOGARITHMS' contains 10 different letters.
| Required number of words | = Number of arrangements of 10 letters, taking 4 at a time. |
| = 10P4 | |
| = (10 x 9 x 8 x 7) | |
| = 5040. |
Discussion:
68 comments Page 2 of 7.
Sann said:
1 decade ago
How can I identify the given question from permutation or combination?
(1)
Shezy said:
1 decade ago
So it means when repetitions not allowed it is an ordering condition ! ?
(1)
Krishan said:
1 decade ago
I dint get it why we are using permutation here? can you explain.
(1)
Appu said:
1 decade ago
I have one doubt that why permutation is used?.
Here mention that repetation not allowed. Permutation is allowed this that is, ab, ba is allowed.
Can anyone help me.
Here mention that repetation not allowed. Permutation is allowed this that is, ab, ba is allowed.
Can anyone help me.
(1)
Habib said:
1 decade ago
It's said 4 letters , and they dont repeat.!!!!.......
Then how come permutations..which actually implies arrangement of the selected letters at a time...
Pls help me, if i am wrong
Then how come permutations..which actually implies arrangement of the selected letters at a time...
Pls help me, if i am wrong
(1)
ARVIND said:
7 years ago
How 4 comes? Please explain.
Arurag said:
9 years ago
The answer is correct. This is a permutation.
i.e npr=n!/(n-r)! Here n! is 10, r is 4.
i.e npr=n!/(n-r)! Here n! is 10, r is 4.
Rishi said:
9 years ago
Here first, we can use 10C4 to find no.of groups containing 4 words. Then by multiplying by !5 we will obtain no.of word arrangements in those groups. In question we have to find words.
Hyndavi said:
9 years ago
They mentioned that no repetition are allowed then how could we use permutations here?
PCB said:
9 years ago
Easier method.
Here, repetition is not allowed. So, to form a word of 4 letters. _ _ _ _.
The 1st letter can be chosen out of 10 letters.
The 2nd letter can be chosen out of the remaining 9 letters. (since no repetition & 1 letter is filled in the 1st position).
The 3rd letter can be chosen out of the remaining 8 letters.
The 4th letter can be chosen out of the remaining 7 letters.
Thus, 10 * 9 * 8 * 7 = 5040.
Here, repetition is not allowed. So, to form a word of 4 letters. _ _ _ _.
The 1st letter can be chosen out of 10 letters.
The 2nd letter can be chosen out of the remaining 9 letters. (since no repetition & 1 letter is filled in the 1st position).
The 3rd letter can be chosen out of the remaining 8 letters.
The 4th letter can be chosen out of the remaining 7 letters.
Thus, 10 * 9 * 8 * 7 = 5040.
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