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Let `a_(1),a_(2),a_(3), . . .` be a harmonic progression with `a_(1)=5anda_(20)=25`. The least positive integer n for which `a_(n)lt0`, is

A

22

B

23

C

24

D

25

Text Solution

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The correct Answer is:
D
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ML KHANNA-PROGRESSIONS -SELF ASSESSMENT TEST
  1. If H be the harmonic mean between x and y, then show that (H+x)/(H-x)+...

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  2. In a H.P., p^(th) term is q and q^(th) term is p then pq^(th) term is

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  3. The harmonic mean of (a)/(1 - ab) and (a)/(1 + ab) is

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  4. If b^(2), a^(2), c^(2) are in A.P., then a + b, b + c, c + a will be i...

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  5. If (x + y)/(2), y ,(y + z)/(2) are in H.P., then x, y, z are in

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  6. If a,b,c are in A.P., then 2^(ax+1),2^(bx+1),2^(cx+1), x in R, are in

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  7. If a, ,b c, are in G.P., then log(a) n, log(b) n, log(c) n are in

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  8. For all ngeq1, prove that 1/(1. 2)+1/(2. 3)+1/(3. 4)+dotdotdot+1/(n(n+...

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  9. The value of underset(i=1)overset(n)sumunderset(j=1)overset(i)sumunde...

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  10. 11^(3)+12^(3)+13^(3)+………….+20^(3) is

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  11. For any integer n ge 1, the sum sum(k=1)^(n) k (k + 2) is equal to

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  12. Find the sum of first n terms of the series 1^(3) + 3^(3) + 5^(3) +…

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

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

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  15. If 100 times the 100th term of an AP with non-zero common difference e...

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  16. Let a(1),a(2),a(3), . . . be a harmonic progression with a(1)=5anda(20...

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  17. Let a1, a2, a3, ,a(100) be an arithmetic progression with a1=3a n dsp...

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  18. Let S(k), where k = 1,2,....,100, denotes the sum of the infinite geom...

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  19. Le a1, a2, a3, ,a(11) be real numbers satisfying a2=15 , 27-2a2>0a n ...

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  20. The sum of first 20 terms of the sequence 0.7,0.77,0.777,"……" is

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