मराठी

There are 10 persons named P1, P2, P3, ... P10. Out of 10 persons, 5 persons are to be arranged in a line such that in each arrangement P1 must occur whereas P4 and P5 do not occur. Find the numb - Mathematics

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प्रश्न

There are 10 persons named P1, P2, P3, ... P10. Out of 10 persons, 5 persons are to be arranged in a line such that in each arrangement P1 must occur whereas P4 and P5 do not occur. Find the number of such possible arrangements.

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उत्तर

Given that P1, P2, P3, ... P10 are 10 persons out of which 5 persons are to be arranged but P1 must occur and P4 and P5 never occur

∴ Selection is to be done only for 10 – 3 = 7 persons

∴ Number of selection = 7C4

= `(7!)/(4!(7 - 4)!)`

= `(7!)/(4!3!)`

= `(7*6*5*4!)/(4!*3*2*1)`

= 35

5 people can be arranged as 5!

So, the number of arrangement = 35 × 5!

= 35 × 120

= 4200

Hence, the required arrangement = 4200.

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पाठ 7: Permutations and Combinations - Exercise [पृष्ठ १२३]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
पाठ 7 Permutations and Combinations
Exercise | Q 12 | पृष्ठ १२३

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