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On the occasion of Dipawali festival ...

On the occasion of Dipawali festival each student of a class sends greeting cards to the others . If there are 20 students in the class , then the total number of greeting cards exchanged by the students is

A

`""^(20)C_2`

B

`2. ""^(20)C_2`

C

`2.""^(20)P_(2)`

D

none

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The correct Answer is:
B
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DIPTI PUBLICATION ( AP EAMET)-PERMUTATIONS & COMBINATIONS-EXERCISE 1B (COMBINATIONS )
  1. The total number of ways of arranging the letters of the word IND...

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  2. Every body in a room shakes with every body clse . The total ...

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  3. On the occasion of Dipawali festival each student of a class s...

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  4. If 36 games were played at a chess tournament with each conte...

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  5. In chess championship 153 games have been played . If a player ...

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  6. Mr. A has c children by his first wife and Ms. B has x+1 chi...

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  7. There are 20 points in plane no three of which are collinear ....

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  8. There are 21 points in a plane no three of which are collinear...

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  9. How many stainght lines can be drawn by joning 10 points on a ...

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  10. There are n points in a plane no three of which are in the same...

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  11. There are n points in a plane no three of which are in the same...

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  12. The number of lines that can be formed from 12 points is a plan...

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  13. Out of thirty points in a plane , eight of them are collinear . T...

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  14. There are 12 points in a plane ,5 only of which are collinear . T...

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  15. The sides AB,BC,CA of a Delta ABC have 3,4and 5 interior poin...

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  16. The number of triangles formed by joining the vertices of a hexag...

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  17. IF T(n) dentoes the number of triangle formed with n points in ...

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  18. Let T(n) be the number of all possible triangles formed by joi...

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  19. Tm denotes the number of triangles that can be formed with the ...

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  20. Given 5 line segments of lengths 2,3,4,5,6 units then the number ...

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