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A person is to count 4500 currency notes...

A person is to count 4500 currency notes, Let `a_n` denote the number of notes he courts in the nth minute. If `a_1=a_2= ........ = a_10 =150` and `a_10, a_11`, ............ are in an A.P. with common difference -2, then the time taken by him to count all notes is :

A

24 minutes

B

34 minutes

C

125 minutes

D

135 minutes .

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MODERN PUBLICATION-SEQUENCES AND SERIES-EXERCISE
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  7. If a geometric progression consisting of positive terms, each term equ...

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  10. If the sum of first n terms of an AP is cn^(2), then the sum of square...

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  11. A person is to count 4500 currency notes, Let an denote the number of ...

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  12. A man saves Rs. 200 in each of the first three months of his service. ...

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  13. Let a(n) be the nth term of an AP, if sum(r=1)^(100)a(2r)= alpha " and...

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  14. The difference between any two consecutive interior angles of a polygo...

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  15. Find the sum Sn of the cubes of the first n terms of an A.P. and show ...

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  16. In a G.P the sum of the first and last terms is 66, the product of the...

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  17. The sum of first ten terms of an A.P. is 155 and the sum of first two ...

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  18. Find three numbers a,b,c between 2 and 18 such that : their sum is 25....

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  19. Find three numbers a,b,c between 2 and 18 such that : their sum is 25....

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  20. Find three numbers a,b,c between 2 and 18 such that : their sum is 25....

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