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If ^nPr=^nP(r+1) and ^nCr=^nC(r-1) then ...

If `^nP_r=^nP_(r+1)` and `^nC_r=^nC_(r-1)` then the values of n,r are

A

n=2, r=3

B

n=3, r=2

C

n=4, r=2

D

n=2, r=4

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The correct Answer is:
B
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PATHFINDER-PERMUTATION AND COMBINATIONS-QUESTION BANK
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  2. If ^9P5=x^9P3 then the value of x will be

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  3. If ^nPr=^nP(r+1) and ^nCr=^nC(r-1) then the values of n,r are

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  4. The value of sum(r=1)^n (^nPr)/(r!) is

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  5. Let Tn denote of the number of triangles which can be formed using the...

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  6. The number of parallelograms that can be formed from a set of four par...

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  7. A polygon has 44 diagonals the number of sides of the polygon is

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  8. In a room each person present shakes hand with the other . If the tota...

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  9. The value of : ^15C1 +^15C3 + ^15C5+…..+ ^15C15 is

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  10. The number of 10 digit numbers formed by using the digits 1&2 is

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  11. The maximum number of trials to open n locks by n keys is 105. Then n...

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  12. The number of circles that can be drawn out of 10 points of which 7 ar...

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  13. The number of different 6-digit numbers that can be formed using the t...

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  14. The number of ways in which 6 different balls can be put in two boxes ...

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  15. If 7 points out of 12 are in same st. line the number of triangles for...

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  16. The total number of 9 digit numbers which have all different digit is

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  17. The number of ways in which 5 letters can be posted in 10 letter boxes...

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  18. The number of five digit telephone numbers none of their digits being ...

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  19. There are 13 stations on a certain railway line.How many kinds of diff...

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  20. Prove that (2n!)/(n!)={1.3.5.....(2n-1)}2^n

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