Home
Class 12
MATHS
The sum of first 21 terms of an A.P. is ...

The sum of first 21 terms of an A.P. is 28 and the sum of the 1st 28 terms is 21. Show that one term of the progression is zero and find the sum of the preceding terms.

Text Solution

Verified by Experts

The correct Answer is:
`28(1)/(2)`
Promotional Banner

Topper's Solved these Questions

  • SEQUENCE AND SERIES

    CHHAYA PUBLICATION|Exercise Exercise 9 C (Multiple Choice Type Questions)|14 Videos

  • SEQUENCE AND SERIES

    CHHAYA PUBLICATION|Exercise Exercise 9 C (Very Short Answer Type Questions)|17 Videos

  • SEQUENCE AND SERIES

    CHHAYA PUBLICATION|Exercise Exercise 9 B (Short Answer Type Questions)|42 Videos

  • SECOND ORDER DERIVATIVE

    CHHAYA PUBLICATION|Exercise Sample Question for Competitive Examination (Assertion-Reason type)|2 Videos

  • SET THEORY

    CHHAYA PUBLICATION|Exercise Assertion-Reason Type|2 Videos

Similar Questions

Explore conceptually related problems

The sum of the first 4 terms of a G.P. is 40 and the sum of first 8 terms is 3280. Obtain the G.P.

If the sum of first n terms of a G.P is p and the sum of the first 2n terms is 3p,show that the sum of first 3n terms is7p.

The sum of first P terms of an A.P. is equal to the sum of its first Q terms. Show that the sum of its first (P+Q) terms is zero.

The sum of first 15 terms of an A.P. is 750 and its first term is 15. Find its 20th term.

The sum of first 6 terms of a G.P. is 9 times the sum of its first 3 terms. Find the common ratio of the G.P.

The sum of first 8 terms of a G.P. is five times the sum of the first 4 terms. Find the common ratio.

Find the sum of first 22 terms, of an A.P. in which d = 7 and 22th term is 149.

If the sum of first n terms of G.P. is S and the sum of its first 2n terms is 5S, then show that the sum of its first 3n terms is 21S.

If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of first n terms.

If the sum of the first n terms of a G.P. = p and the sum of the first 2n terms = 3p, show that the sum of first 3n terms = 7p.

CHHAYA PUBLICATION-SEQUENCE AND SERIES-Exercise 9 B (Long Answer Type Questions)
  1. The sum of first 21 terms of an A.P. is 28 and the sum of the 1st 28 t...

    Text Solution

    |

  2. If the sum of first 2n terms of the A.P. 2, 5, 8,…. Is equal to the su...

    Text Solution

    |

  3. Let S(n) be the sum of first n terms of an A.P. If S(2n) = 5s(n), then...

    Text Solution

    |

  4. The sum of the first p terms of an A.P. is q and the sum of the first ...

    Text Solution

    |

  5. If the pth and qth terms of an A.P. be a and b respectively, show that...

    Text Solution

    |

  6. If S(1), S(2), S(3) be the sums of n terms of three aA.P.'s, the first...

    Text Solution

    |

  7. If the sums of n, 2n and 3n terms of an A.P. be S(1), S(2), S(3) respe...

    Text Solution

    |

  8. The sums of n terms of two A.P.'s are in the ratio (4n-13) : (3n + 10)...

    Text Solution

    |

  9. The sums of first n terms of two A.P.'s are in the ratio (3n+5) : (5n ...

    Text Solution

    |

  10. Insert a number of arithmetic means between 4 and 34 such that the sum...

    Text Solution

    |

  11. If a, b, c are in A.P. then show that, a((1)/(b)+(1)/(c )), b((1)/(c )...

    Text Solution

    |

  12. Three positive numbers a, b, c are in A.P. Prove that (1)/(sqrt(b)+sqr...

    Text Solution

    |

  13. If a(1), a(2), a(3),…, a(n) be in A.P. Show that, (1)/(a(1)a(2)) + (...

    Text Solution

    |

  14. If a(1), a(2), a(3),…, a(2k) are in A.P., prove that a(1)^(2) - a(2)^(...

    Text Solution

    |

  15. If (b-c)^(2), (c-a)^(2), (a-b)^(2) are in A.P. then prove that, (1)/(b...

    Text Solution

    |

  16. Find the sum to n terms of each of the following series : 2.4 + 6.8 ...

    Text Solution

    |

  17. Find the sum to n terms of each of the following series : 1^(2) + 3^...

    Text Solution

    |

  18. Find the sum to n terms of each of the following series : 1.3 .5 + 3...

    Text Solution

    |

  19. Find the sum of the following series : 3.1^(2) + 4.2^(2) + 5.3^(2) +...

    Text Solution

    |

  20. Find the sum of the following series : 1+3+6+10+15+… to n terms.

    Text Solution

    |