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  • Out of a group of 10 students, 4 has to deliver a speech one by one in order . But out of these 10, two students are not to be included. Then the number of ways in which speech can b

Out of a group of 10 students, 4 has to deliver a speech one by one in order . But out of these 10, two students are not to be included. Then the number of ways in which speech can be delivered is 

Option: 1

1440 


Option: 2

1680 


Option: 3

1920 


Option: 4

2125 


Answers (1)

best_answer

As we have learned

Rule of Restricted Permutations

The number of permutations of n dissimilar things takes r at a time when p particular things never occur is ^{n-p}C_{r} \,. \,r!

 

Now,

Since, two are not to be included, so all 4 have to be selected out of 8 only. 

Its number of ways ^8 C _4 = 70

 Now, those selected four can speak in 4 ! ways 

Total number of ways = 70 * 24 = 1680 

 

Posted by

shivangi.shekhar

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