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If the number of combinations of n diffe...

If the number of combinations of n different things taken (r+r) at a time be equal to the number of combinations taken (r-r) at a time , find the value of n.

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The correct Answer is:
n= 2r
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CHHAYA PUBLICATION-PERMUTATION AND COMBINATION -EXERCISE 7B ( Short Answer Type Questions )
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  5. There are 15 points in a plane of which 4 points lie in one stright li...

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  8. If the number of combinations of n different things taken (r+r) at a t...

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  9. In how many ways can a person contribute to a charitabe fund out of 10...

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  10. Find the number of factors of 37800 .

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  11. Find the number of different factors of 3528 which are greater than 1 ...

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  12. Eight questions are given , each question has an alternative Prove tha...

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  13. Prove that the total number of selections that can be made out of the ...

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  14. In how many different ways ten 10 paise and five 5- paise coins can be...

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  15. From 10 boys and 6 girls , how many different selections can be made s...

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  16. The results (win , loss or draw ) of 10 fooball matches are to be pred...

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  17. If the ratio of the total number of combinations of 2n different thing...

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  18. In how many ways can one or more fruits be selected from 4 apples ,5 o...

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  19. Let t(n) denote the number of diagonals of a polygon of n sides . If ...

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