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If a1=1 and an =na(n-1), for all positiv...

If `a_1=1` and `a_n =na_(n-1)`, for all positive integers `n ge 2`, then `a_5` is equal to :

A

125

B

120

C

100

D

24

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MODERN PUBLICATION-SEQUENCES AND SERIES-EXERCISE
  1. If a, b, c are in G.P. and x, y are arithmetic mean of a, b and b, c r...

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  2. A student read common difference of an A.P. as -3 instead of 3 and obt...

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  3. If a1=1 and an =na(n-1), for all positive integers n ge 2, then a5 is ...

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  4. If a1, a2, ............, an are in A.P.with common difference d ne 0, ...

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  5. The arithmetic mean of first n odd natural numbers is :

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  6. In a sequence of 21 terms the first 11 terms are in A.P. with common d...

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  7. If the sum to 2n terms of the A.P. 2, 5, 8, 11, .... is equal to the s...

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  8. The third term of a GP is 3. What is the product of the first five ter...

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  9. If the sum of the first two terms and the sum of the first four terms ...

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  10. If n> 1 and log2 x,log3 x, logx 16, are in G.P., then what is x equal ...

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  11. In a geometric progression with first term a and common ratio r, what ...

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  12. The harmonic mean of two numbers is 21.6. If one of the numbers is 27,...

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  13. Given that alpha,gamma are roots of the equation A x^2-4x+1=0,a n dbet...

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  14. Consider an infinite geometric series with first term a and common rat...

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  15. Sum of the n terms of the series (3)/(1^(2))+(5)/(1^(2)+2^(2))+(7)/(1^...

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  16. Let alpha and beta be the roots of x^2-x+p=0 and gamma and delta be th...

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  17. Let the positive numbers a, b, c, d be in A.P. Then abc, abd, acd, bcd...

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  18. If the sum to 2n terms of the A.P. 2, 5, 8, 11, .... is equal to the s...

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  19. Suppose a,b,c are in AP and a^(2),b^(2),c^(2) are in GP, If agtbgtc an...

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  20. 5th term of a G.P. is 2, then the product of first 9 terms is:

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