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If ""^(n)P(r)=5040 and ""^(n)C(r)=210, f...

If `""^(n)P_(r)=5040 and ""^(n)C_(r)=210,` find n and r.

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The correct Answer is:
n=10, r=4
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AAKASH SERIES-PERMUTATIONS & COMBINATIONS-EXERCISE -1.5 VERY SHORT ANSWER QUESTIONS
  1. Find the value of ""^(10)C(5)+2. ""^(10)C(4)+""^(10)C(3).

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  2. Simplify ""^(34)C(5)+ overset(4) underset(r=0)Sigma ""^((38-r))C(4).

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  3. If ""^(n)P(r)=5040 and ""^(n)C(r)=210, find n and r.

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  4. Find the number of ways of selecting 7 members from a contingent of 10...

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  5. Find the number of ways of selecting 3 girls and 3 boys out of 7 girls...

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  6. Find the number of ways of selecting 3 vowels and 2 consonants from th...

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  7. Find the number of ways of selecting 4 English, 3 Telugu and 2 Hindi b...

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  8. Find the number of ways of selecting a committee of 6 members out of 1...

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  9. Find the number of ways of selecting 5 books from 9 different mathemat...

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  10. The number of five letter words can be formed using 3 consonent...

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  11. 10 persons are sitting in a row. Find the number of ways of selecting ...

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  12. 10 persons are sitting around a circle. In how many ways can 2 persons...

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  13. If a set of 'm' parallel lines intersect another set of 'n' parallel l...

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  14. Find the number of diagonals of a polygon with 12 sides.

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  15. If there are 5 alike pens, 6 alike pencils and 7 alike erasers, find t...

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  16. Find the number of positive divisors of 1080

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  17. Find the number of ways of dividing 80 persons into 3 groups containin...

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  18. Find the number of ways in which 12 things be (i) divided into 4 equal...

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  19. Find the number of ways in which 12 things be (i) divided into 4 equal...

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  20. To pass an examination a student has to pass in each of the three pape...

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