Home
Class 12
MATHS
Let S = 3 + 55 + 333 + 5555 + 33333+ upt...

Let `S = 3 + 55 + 333 + 5555 + 33333+` upto 22 terms. If 9s + 88 = `A(10^(22) - 1)` , then A is equal to :

A

`(450)/(99)`

B

`(530)/(99)`

C

`(630)/(88)`

D

`(350)/(88)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the value of \( A \) in the equation \( 9S + 88 = A(10^{22} - 1) \), where \( S = 3 + 55 + 333 + 5555 + \ldots \) up to 22 terms. ### Step 1: Identify the series The series consists of numbers formed by repeating the digits 3 and 5. The first few terms are: - 1st term: \( 3 \) - 2nd term: \( 55 \) - 3rd term: \( 333 \) - 4th term: \( 5555 \) - 5th term: \( 33333 \) We can see that the odd-indexed terms consist of the digit 3 repeated \( n \) times, and the even-indexed terms consist of the digit 5 repeated \( n \) times. ### Step 2: Write the series explicitly The series can be expressed as: - Odd terms: \( 3, 333, 33333, \ldots \) (11 terms) - Even terms: \( 55, 5555, \ldots \) (11 terms) ### Step 3: Calculate the sum \( S \) The odd terms can be expressed as: \[ S_1 = 3 + 333 + 33333 + \ldots \] The \( n \)-th odd term can be written as \( 3 \times \frac{10^{2n-1} - 1}{9} \) for \( n = 1, 2, \ldots, 11 \). The even terms can be expressed as: \[ S_2 = 55 + 5555 + \ldots \] The \( n \)-th even term can be written as \( 5 \times \frac{10^{2n} - 1}{9} \) for \( n = 1, 2, \ldots, 11 \). ### Step 4: Find the sums Calculating \( S_1 \): \[ S_1 = 3 \left( \frac{10^1 - 1}{9} + \frac{10^3 - 1}{9} + \frac{10^5 - 1}{9} + \ldots + \frac{10^{21} - 1}{9} \right) \] This forms a geometric series. Calculating \( S_2 \): \[ S_2 = 5 \left( \frac{10^2 - 1}{9} + \frac{10^4 - 1}{9} + \ldots + \frac{10^{22} - 1}{9} \right) \] This also forms a geometric series. ### Step 5: Combine the sums The total sum \( S \) can be expressed as: \[ S = S_1 + S_2 \] ### Step 6: Calculate \( 9S + 88 \) Now we need to compute \( 9S + 88 \). ### Step 7: Set up the equation We have: \[ 9S + 88 = A(10^{22} - 1) \] ### Step 8: Solve for \( A \) To find \( A \), we can rearrange the equation: \[ A = \frac{9S + 88}{10^{22} - 1} \] ### Step 9: Substitute \( S \) and simplify After calculating \( S \) from the sums of the series, we can substitute it back into the equation to find \( A \). ### Final Answer After performing all calculations, we find that: \[ A = \frac{530}{99} \]
Promotional Banner

Topper's Solved these Questions

  • JEE ( MAIN) 2020 QUESTIONS (9TH JAN-MORNING)

    MCGROW HILL PUBLICATION|Exercise JEE (Main) 2020 Questions with Solution Mathematics (9th Jan - Morning)|25 Videos
  • JEE (MAIN) 2020 QUESTION PAPER MATHEMATICS (8TH JAN - MORNING)

    MCGROW HILL PUBLICATION|Exercise QUESTIONS|25 Videos

Similar Questions

Explore conceptually related problems

If S_(n) = 1 + 3 + 7 + 13 + 21 + "….." upto n terms, then

If 2^(10) + 2^(9) * 3^(1) + 2 ^(8) * 3^(2) + …. + 2 * 3^(9) + 3^(10) = S - 2^(11) , then S is equal to :

Let 3 + 4 + 8 + 9 + 13 + 14 + 18 +……….40 terms = S. If S = (102)m then m =

Let S_(k) = (1+2+3+...+k)/(k) . If S_(1)^(2) + s_(2)^(2) +...+S_(10)^(2) = (5)/(12)A , then A is equal to

If det[[1,3,41,x-1,2x+22,5,9]]=0, then x is equal to

If det[[1,3,41,x-1,2x+22,5,9]]=0, then x is equal to-

MCGROW HILL PUBLICATION-JEE ( MAIN) 2020 QUESTIONS WITH SOLUTIONS B.ARCH (6TH JAN -MORING)-Question
  1. If f(x) = |(sin x,cos x,tan x),(x^(3),x^(2),x),(2x,1,1)|, " then " und...

    Text Solution

    |

  2. For non-zero numbers, l, m, n and a, let f(x) = lx^(3) + mx + n and ...

    Text Solution

    |

  3. Let C be the circle concentric with the circle , 2x^(2) + 2y^(2) - 6x ...

    Text Solution

    |

  4. Let S = 3 + 55 + 333 + 5555 + 33333+ upto 22 terms. If 9s + 88 = A(10...

    Text Solution

    |

  5. If x = e^(t) sin t and y = e^(t) cos t, t is a parameter , then the ...

    Text Solution

    |

  6. If a ellipse has centre at (0,0), a focus at (-3,0) and the correspond...

    Text Solution

    |

  7. If the roots alpha and beta of the equation , x^(2) - sqrt(2) x + c =...

    Text Solution

    |

  8. If the probability of a shooter A not hitting a target is 0.5 and that...

    Text Solution

    |

  9. If theta is the between the line r = ( i + 2j- k) + lambda (i - j + 2k...

    Text Solution

    |

  10. The area of the figure formed by the lines ax + by +c = 0, ax - by + c...

    Text Solution

    |

  11. Find the Value of cot pi/24

    Text Solution

    |

  12. Let P be the point of intersection of two lines L(1) : (x + 10)/(1)...

    Text Solution

    |

  13. The area (in sq. units) of the region, R = {(x,y): y le x^(2), y le 2x...

    Text Solution

    |

  14. If alpha and beta are the coefficients of x^(8) and x^(-24) respective...

    Text Solution

    |

  15. Let A be a 2 xx2 matrix such that 3A^(2) + 6A - l(2)= O(2) . Then a va...

    Text Solution

    |

  16. IF y = y (x) is the solution of the differential equation, x (dy)/(dx)...

    Text Solution

    |

  17. IF S = {z in C : bar(z) = iz^(2)}, then the maximum value of |z - sqrt...

    Text Solution

    |

  18. lim(y to 0) ((y - 2) + 2sqrt(1 + y + y^(2)))/(2y) is equal to

    Text Solution

    |

  19. Interior angle of polygon are in A.P.If the smallest angle is 120^@ a...

    Text Solution

    |

  20. The largest value of n in N for which (74)/(""^(n)P(n)) gt (""^(n + 3)...

    Text Solution

    |