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Class - 10 (Mixed problem on permutation and combination - 3)
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Class - 10 (Mixed problem on permutation and combination - 3)

## Bharat Gupta is teaching live on Unacademy Plus

Bharat Gupta
Engineer by degree Mathematician by Heart. Having 22 years of teaching experience. Visit my youtube channel BHARAT GUPTA-RADIX .

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In 2nd question there is not any compulsion of taking the two together occuring things to be always taken. Eg. let 6 letters ABCDEF be given and we have to find 4 digit words in which AB occur together. Is this question means we have to self understand that AB will always be present in every word or there may be a situation where AB itself is not present and rest 4 letters make words 4C4 * 4! permutation
Ishita P
5 months ago
As per your question, it means that AB will always be present in the word. Therefore, the answer will be 4C2 * 4!
AT
Sir, there is a much simpler and shorter way of solving the first question. || P _ _ _ _ S _ _ _ _ _ _ || 10!/2! * 2 * 7 = 25401600 || Explanation: 10!/2! - To fill in the blanks with 10 letters (12 - P & S) with two like letters. || 2 - Because it could be P _ _ _ _ S or S _ _ _ _ P. || 7 - Because the (P _ _ _ _ S) part can be positioned at total 7 places by moving it to the right.
Bharat Gupta
7 months ago
Yes you are correct
Is there a compulsion that these two things that have been kept away from the N have to be included in the arrangement?
Akanksha Gupta
a year ago
Can there not be (N-2)C(R)?
Bharat Gupta
a year ago
Please mention the time in the video where u have problem
Akanksha Gupta
a year ago
8:01 Is there a compulsion that the two things which occur together have to be selected? can't there be a case where they if they are selected then they occur together, if they aren't selected then we have (N-2)C(R) as a case as well.
1. COMBINATION Permutation and combination mixed Problem part- 3 Follow Upvote

2. Problem for this lesson In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 Find the number of permutation of n different things taken r at a time such that two specified things occur together? a/C.* r! x (r- 1)! x 2

3. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400

4. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400

5. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 PERm UTATIO NS waHs

6. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 PSTT E 9

7. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 PSTT E 9

8. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 Totow

9. In how many ways can the letters of the word PERMUTATIONS can be arranged if there are 4 letters between P and S? a. 23421600 b. 25401600 c. 23412600 d. 25514400 2

10. Find the number of permutation of n different things taken r at a time such that two specified things occur together? x(r 2)

11. Find the number of permutation of n different things taken r at a time such that two specified things occur together? a."C, x r! No vo aoruw too -) cn be

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