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In an A.P., if a = 1 , a(n) = 20 and S(n...

In an A.P., if a = 1 , `a_(n) = 20` and `S_(n) = 399`, then n = ……..

A

19

B

42

C

28

D

38

Text Solution

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The correct Answer is:
D
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VGS PUBLICATION-BRILLIANT-PROGRESSIONS-Part - B Observation bits to solve various bits (Given in the public examination)
  1. The 21^(th) of an A.P., whose first two terms are -3 and 4 is ………..

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  2. The common difference of an A.P. for which a(18)-a(14) = 32 is …….

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  3. In an A.P., if a = 1 , a(n) = 20 and S(n) = 399, then n = ……..

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  4. Which term of the G.P. 1/3, 1/9, 1/27,………. is 1/(2187)?

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  5. Which term of A.P., 18,15,12,……. Equal to '0' ?

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  6. If k, 2k+1, 2k+3 are three consecutive terms in A.P., then find the va...

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  7. If a(n) = (n)/(n+1), then a(2017) = ………..

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  8. n^(th) term of a progression a, ar ar^(2), ………. is …………

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  9. IF 4,a,9 are in G.P., then a=………..

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  10. The next term in A.P., sqrt(3), sqrt(12), sqrt(27) is ……..

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  11. The common difference of A.P. log(2) 2, log(2)4, log(2)8, is …………..

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  12. The sum of first 'n' odd natural numbers is ………

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  13. Determine the AP whose 3^(rd) term is 5 and the 7^(th) term is 9.

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  14. If (i) -1.0 , -1.5, -2.0, -2.5, ……… and (ii) -1, -3, -9, -27, ……. are ...

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  15. Which of the following is a GP has the common ratio as sqrt(2)?

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  16. The common difference of an Arithmetic Progression in which a(25) - a(...

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  17. Sum of 10 terms of the progression log 2 + log 4 + log 8 + log 6 + …. ...

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  18. Which term of the Arithmetic Progression 24, 21, 18, ……. Is the first ...

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  19. The sum of first 100 natural numbers is ………….

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  20. If a, b, c are in G.P., then b =

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