a geometric progression has a third term of 20 and a sum to infinity which is three times the first term. find the first term

  1. 👍 5
  2. 👎 0
  3. 👁 1,504
  1. Is this a follow up from your previous question?

    term(3) = ar^2 = 20
    a = 20/r^2

    a/(1-r) = 3a
    1/(1-r) = 3
    same as in your previous post, r = 2/3

    then a = 20/(4/9(
    = 20(9/4) = 45

    your sequence is 45 , 30 , 20 , 40/3 , 80/9 , ...
    is the third term 20 ? , YES
    sum of all terms = 20/(1-2/3)
    = 20/(1/3)
    = 60 , which is 3 times the first term.
    All is good!

    1. 👍 5
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. maths

    the sum of the 4th and 6th terms of an A.P is 42. the sum of the 3rd and 9th terms of the progression is 52. find the first term, the common difference and the sum of the first ten terms of the progression.

  2. Arithmetic

    The first, second and third terms of a geometric progression are 2k+3, k+6 and k, respectively. Given that all the terms of geometric progression are positive, calculate (a) the value of the constant k (b) the sum to infinity of

  3. Maths

    a geometric progression has the second term as 9 and the fourth term as 81. find the sum of the first four terms.?

  4. uniuyo

    The second and fifth term of a geometric progression are 21 and 567 respectively. Find the first term and the common ratio of the progression

  1. Maths

    The sum of n numbers of geometric progression is GP=(2^n+1)-1. Find the first term and the common difference.

  2. quine

    The 2nd and 5th term of a geometric progression are - 6 & 48 find the sum of the first four term respectively

  3. math

    Three numbers form a geometric progression. If the second term is increased by 2, then the progression will become arithmetic and if, after this, the last term is increased by 9, then the progression will again become geometric.

  4. Maths

    A Geometric progression X has a first term of 4a and its sixth term is 256. Another Geometric progression Y has a first term of 3a and its fifth term is 48. Find the: (i) First term of X (ii) Sum of the first four terms of X

  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

  2. Algebra

    The first term of an A.P is 3 and the fifth term is 9.Find the number of terms in the progression if the sum of the progression is 81.

  3. math

    find the sum of the first 8th term of the Geometric progression, 1,3,9,27

  4. math

    The 3rd term of a geometric progression is nine times the first term.if the second term is one-twenty fourth the 5th term.find the 4th term. solution ar^2=9a r=sqr of 9 r=3.pls help me on how to get the first term(a)

You can view more similar questions or ask a new question.