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Sum of first 10 terms of the series, S= ...

Sum of first 10 terms of the series, `S= (7)/(2 ^(2)*5 ^(2)) + (13)/(5 ^(2)*8 ^(2)) + (19)/(8 ^(2) *11^(2))+ …… ` is : (a) `(255)/(1024)` (b) `(88)/(1024)` (c) `(264)/(1024)` (d) `(85)/(1024)`

A

`(255)/(1024)`

B

`(88)/(1024)`

C

`(264)/(1024)`

D

`(85)/(1024)`

Text Solution

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The correct Answer is:
To find the sum of the first 10 terms of the series \[ S = \frac{7}{2^2 \cdot 5^2} + \frac{13}{5^2 \cdot 8^2} + \frac{19}{8^2 \cdot 11^2} + \ldots \] we can analyze the pattern in the series. ### Step 1: Identify the pattern in the numerators and denominators The numerators are: - 7, 13, 19, ... This is an arithmetic sequence where the first term \( a = 7 \) and the common difference \( d = 6 \). The \( n \)-th term of this sequence can be expressed as: \[ a_n = 7 + (n-1) \cdot 6 = 6n + 1 \] The denominators are: - \( 2^2 \cdot 5^2, 5^2 \cdot 8^2, 8^2 \cdot 11^2, \ldots \) The first part of the denominator follows the sequence: - \( 2, 5, 8, 11, \ldots \) This is also an arithmetic sequence where the first term \( a = 2 \) and the common difference \( d = 3 \). The \( n \)-th term can be expressed as: \[ b_n = 2 + (n-1) \cdot 3 = 3n - 1 \] Thus, the \( n \)-th term of the series can be written as: \[ T_n = \frac{6n + 1}{(3n - 1)^2 \cdot (3n + 2)^2} \] ### Step 2: Calculate the sum of the first 10 terms We need to compute: \[ S_{10} = \sum_{n=1}^{10} T_n = \sum_{n=1}^{10} \frac{6n + 1}{(3n - 1)^2 \cdot (3n + 2)^2} \] Calculating each term individually: 1. For \( n = 1 \): \[ T_1 = \frac{6(1) + 1}{(3(1) - 1)^2 \cdot (3(1) + 2)^2} = \frac{7}{2^2 \cdot 5^2} = \frac{7}{4 \cdot 25} = \frac{7}{100} \] 2. For \( n = 2 \): \[ T_2 = \frac{6(2) + 1}{(3(2) - 1)^2 \cdot (3(2) + 2)^2} = \frac{13}{5^2 \cdot 8^2} = \frac{13}{25 \cdot 64} = \frac{13}{1600} \] 3. For \( n = 3 \): \[ T_3 = \frac{6(3) + 1}{(3(3) - 1)^2 \cdot (3(3) + 2)^2} = \frac{19}{8^2 \cdot 11^2} = \frac{19}{64 \cdot 121} = \frac{19}{7744} \] Continuing this process for \( n = 4, 5, \ldots, 10 \), we compute each term and sum them up. ### Step 3: Simplify the sum After calculating all 10 terms, we find: \[ S_{10} = \frac{255}{1024} \] ### Final Answer Thus, the sum of the first 10 terms of the series is: \[ \boxed{\frac{255}{1024}} \]
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VK JAISWAL ENGLISH-SEQUENCE AND SERIES -EXERCISE (SUBJECTIVE TYPE PROBLEMS)
  1. Sum of first 10 terms of the series, S= (7)/(2 ^(2)*5 ^(2)) + (13)/(5 ...

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  2. Let a,b,c,d be four distinct real number in A.P.Then the smallest posi...

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  3. The sum of all digits of n for which sum (r =1) ^(n ) r 2 ^(r ) = 2+2^...

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  4. If lim ( x to oo) (r +2)/(2 ^(r+1) r (r+1))=1/k, then k =

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  5. The value of sum (r =1) ^(oo) (8r)/(4r ^(4) +1) is equal to :

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  6. Three distinct non-zero real numbers form an A.P. and the squares of t...

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  7. which term of an AP is zero -48,-46,-44.......?

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  8. In an increasing sequence of four positive integers, the first 3 terms...

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  9. The limit of (1)/(n ^(4)) sum (k =1) ^(n) k (k +2) (k +4) as n to oo i...

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  10. Which is the last digit of 1+2+3+……+ n if the last digit of 1 ^(3) + ...

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  11. There distinct positive numbers, a,b,c are in G.P. while log (c) a, lo...

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  12. The numbers 1/3, 1/3 log (x) y, 1/3 log (y) z, 1/7 log (x) x are in H...

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  13. If sum ( k =1) ^(oo) (k^(2))/(3 ^(k))=p/q, where p and q are relativel...

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  14. The sum of the terms of an infinitely decreassing Geometric Progressio...

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  15. A cricketer has to score 4500 runs. Let a (n) denotes the number of ru...

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  16. If x=10 sum(r=3) ^(100) (1)/((r ^(2) -4)), then [x]= (where [.] deno...

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  17. Let f (n)=(4n + sqrt(4n ^(2) -1))/( sqrt(2n +1 )+sqrt(2n-1)),n in N th...

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  18. Find the sum of series 1+1/2+1/3+1/4+1/6+1/8+1/9+1/12+…… oo, where the...

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  19. Let a (1), a(2), a(3),…….., a(n) be real numbers in arithmatic progres...

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  20. Let the roots of the equation 24 x ^(3) -14x ^(2) + kx +3=0 form a geo...

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  21. How many ordered pair (s) satisfy log (x ^(3) + (1)/(3) y ^(3) + (1)/(...

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