Home
Class 12
MATHS
If (5+9+13+..."upto n terms")/(7+9+11+.....

If `(5+9+13+..."upto n terms")/(7+9+11+..."upto 12 terms")=(5)/(12)`, then n is equal to

A

5

B

6

C

9

D

12

Text Solution

Verified by Experts

The correct Answer is:
B
Let `S_(1)=5+9+13+...+n" terms"`
`impliesS_(1)=(n)/(2)[2xx5+(n-1)4]`
`=n(3+2n)`
and `S_(2)=7+9+11+...+12`
terms `=(12)/(2)[2xx7+(12-1)2]`
`=6(36)=216`
Since, `(S_(1))/(S_(2))=(5)/(12)" "["given"]`
`implies" "(n(3+2n))/(216)=(5)/(12)`
`implies" "2n^(2)+3n-90=0`
`implies(2n+15)(n-6)=0impliesn=6`
[since, n cannot be negative]
Promotional Banner

Topper's Solved these Questions

  • PRACTICE SET 13

    MHTCET PREVIOUS YEAR PAPERS AND PRACTICE PAPERS|Exercise PAPER II OBJECTIVE TYPE|50 Videos

  • PRACTICE SET 15

    MHTCET PREVIOUS YEAR PAPERS AND PRACTICE PAPERS|Exercise PAPER 2 (MATHEMATICS)|50 Videos

Similar Questions

Explore conceptually related problems

If (1 + 3 + 5 + .... " upto n terms ")/(4 + 7 + 10 + ... " upto n terms") = (20)/(7 " log"_(10)x) and n = log_(10)x + log_(10) x^((1)/(2)) + log_(10) x^((1)/(4)) + log_(10) x^((1)/(8)) + ... + oo , then x is equal to

If (3+5+7+... upto n terms )/(5+8+113... upto 10 terms )=7, then find the value of n.

If (5 + 9 + 13 + .... rarr nterms) / (7 + 9 + 11 + ... rarr (n + 1) terms) = (17) / (16), then n =

if (3 +5+7+9+…. " up to 35 terms " )/(5+8+11+ …. " up to n terms ")=7 , find the value of n.

If (3+5+7+ . . . .+"n terms")/(5+8+11+ . . .. +"10 terms")=7 , then the value of n, is

Consider two arithmetic progressions 3, 8, 13, ,...... upto 37 terms 3, 9, 15, 21, ...... upto 25 terms Find the number of common terms in there two series.

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

(1)/(3.5)+(1)/(5.7)+(1)/(7.9)+…….. up to n terms is equal to

MHTCET PREVIOUS YEAR PAPERS AND PRACTICE PAPERS-PRACTICE SET 14-Paper 2 (Mathematics)
  1. The equation of circle which touches the line y=x at origin and passe...

    Text Solution

    |

  2. The measure of the chord intercepted by circle x^2 + y^2 = 9 and the l...

    Text Solution

    |

  3. If (5+9+13+..."upto n terms")/(7+9+11+..."upto 12 terms")=(5)/(12), th...

    Text Solution

    |

  4. The number of solutions of the pair of equations 2s in^2theta-cos2thet...

    Text Solution

    |

  5. If sin4A-cos2A=cos4A-sin2A ("where",0ltAlt(pi)/(4)), then the value...

    Text Solution

    |

  6. Solve the differential equation (dy)/(dx)=(x(2logx+1))/((siny+ycosy)).

    Text Solution

    |

  7. If sin(sin^(-1)1/5+cos^(-1)x)=1, then find the value of xdot

    Text Solution

    |

  8. In a DeltaABC, (b+c)(bc)cosA+(a+c)(ac)cosB+(a+b)(ab)cosC is

    Text Solution

    |

  9. f(x)=(e^(2x)-1)/(e^(2x)+1) is

    Text Solution

    |

  10. Find the length of normal to the curve x=a(theta+sintheta),y=a(1-costh...

    Text Solution

    |

  11. If y=(x+sqrt(1+x^2))^n then (1+x^2)(d^2y)/(dx^2)+x(dy)/(dx)

    Text Solution

    |

  12. (d)/(dx)[log(e)e^(sin(x^(2)))] is equal to

    Text Solution

    |

  13. The area enclosed between the curve y=log(e)(x+e) and the coordinate a...

    Text Solution

    |

  14. If f(x)={{:((1-sinx)/(pi-2x),,","xne(pi)/(2)),(lambda,,","x=(pi)/(2)):...

    Text Solution

    |

  15. The value of lim(xto0) ((1-cos2x)sin5x)/(x^(2)sin3x) is

    Text Solution

    |

  16. The differential equation of the family of parabolas with focus at the...

    Text Solution

    |

  17. int(-2)^(2)sin^(3)x|x|dx is equal to

    Text Solution

    |

  18. Find the antiderivative of f(x) = In (In x) + (In x)^-2 whose graph p...

    Text Solution

    |

  19. A basket contains 5 apples and 7 oranges and another basket contains 4...

    Text Solution

    |

  20. For the following linear programming problem minimize Z=4x+6y subject ...

    Text Solution

    |