arithmetic

What is the sum to 15 terms of an arithmetic progression whose 8th term is 4?

  1. 👍 0
  2. 👎 0
  3. 👁 42
asked by vinay
  1. W.k.t,
    Sn = n/2 {2a + (n-1)d} then
    S15 = 15/2 {2a + 14d}
    =15/2 {2(a+7d)}
    wkt, a+7d = 15
    S15 = 15(15)=225

    1. 👍 0
    2. 👎 0
    posted by subbu

Respond to this Question

First Name

Your Response

Similar Questions

  1. math

    The 3rd term of an Arithmetic Progression is 10 more than the first term while the fifth term is 15 more than the second term. Find the sum of the 8th and 15th terms of the Arithmetic Progression if the 7th term is seven times the

    asked by Toba on May 8, 2016
  2. Maths

    1) In the arithmetic progression, the 8th term is twice the 4th term and the 20th term is 40. Find the common difference and the sum of the terms from the 8th to the 20th term inclusive. 2) Find the least number of terms of the

    asked by Anonymous on April 17, 2008
  3. Maths

    1..The first 2 terms of a geometric progression are the same as the first two terms of an arithmetic progression.The first term is 12 and is greater than the second term.The sum of the first 3 terms od the arithmetic progression

    asked by Lucas on February 3, 2013
  4. maths

    1) The first term of arithmetic progression is -20 and the sum of it's term is 250. find it's last term if the number of it's terms is 10 2) Find the fifth term from the arithmetic progression -12, -9, -6 hence find the sum of

    asked by Amir khan on September 25, 2011
  5. math

    The first, the third and the seventh terms of an increasing arithmetic progression are three consecutive terms of a geometric progression. In the first term of the arithmetic progression is 10 find the common difference of the

    asked by kudu on February 2, 2015
  6. math C2 sequences and series

    The eight,fourth and second terms of an arithmetic progression form the first three terms of a geometric series. The arithmetic progression has first term A and common difference d, and the geometric progression has first term G

    asked by Stephan on January 2, 2017
  7. math

    An arithmetic progression as the same first and second terms as the geometric progression. Find the sum of the first 20 terms of the arithmetic progression. How do I do this? I tried to find the common ratio for G.P. and then

    asked by lin on September 14, 2016
  8. math

    in a Geometric progression the sum of the first and the second terms is 90 and the sum of the second and the fourth terms is equal to 30.find the sum of the first 8th term in the progression

    asked by Ali on November 5, 2010
  9. AP Calculus

    The 9th term of an arithmetic progression is 4+5p and the sum of the four terms of the progression is 7p-10, where p is a constant. Given that common difference of the progression is 5, find the value of p.

    asked by Watermelon on November 30, 2011
  10. Precalculus

    The 8th term in an arithmetic sequence is 5, and the sum of the first 10 terms is 20. Find the common difference and the first term of the sequence. Alright so in an arithmetic squence the difference d between any two successive

    asked by Trudy on January 20, 2007

More Similar Questions