Math

The fourth term of a geometric series is 30; the ninth term is 960. Determine the sum of the first nine terms. How do I find t1 and r?

  1. 👍
  2. 👎
  3. 👁
  1. Just translate the English using your definitions of a GS
    ar^3 = 30
    ar^8 = 960

    divide the 2nd by third, the a's will cancel
    r^5 = 32
    r = 2

    in ar^3 = 30
    a(8) = 30
    a = 15/4

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. math

    Determine whether each sequence is arithmetic or geometric. Find the next three terms. 1. 14, 19, 24, 29, . . . (1 point) geometric, 34, 39, 44 arithmetic, 32, 36, 41 arithmetic, 34, 39, 44 *** The sequence is neither geometric

  2. Alg 2

    The first term of a geometric sequence is 25, and the fourth term is 1\5. (a) Find the common ratio r. r = Find the fifth term. a5 = (b) Find the partial sum of the first eight terms. S8 =

  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. 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 B30

    If the seventh term of a geometric series is 192, and the first term is 3, find the sum of the first 8 terms of the series

  2. mathematics

    in a geometric progression, the first term is a and the common ratio is r. the sum of the first two terms is 12 and the third term is 16. a) determine the ratio (ar^2)/a+ar( aready found the answer as 4/3) b) if the first term is

  3. Math

    1. Find the 11th term of the geometric sequence 64, -32, 16, -8, … . 2. Find the 1st term of a geometric sequence with a 10th term -1024 and r = -2. 3. Find the sum of each infinite geometric series, if possible. a. 10 + 2 + 2/5

  4. math

    Find the sum to 5 terms of the geometric progression whose first term is 54 and fourth term is 2

  1. Arithmetic Sequence

    Given the third term of an arithmetic sequence less than the fourth term by three. The seventh term is two times the fifth term. Find the common difference and the first term.

  2. math

    the third term of a geometric sequence is t3= -75 and the sixth term is t6= 9375. determine the first term and the common ratio

  3. maths

    the third term of a geometric sequence is 6 and the sixth term is 3 over 32. Determine the first terms and the general term Tn?

  4. mathematics

    A goemetric progression is such that the 3rd term is 9times the first term ,while the 2nd term is one-twenty fourth of the 5th term.Find the 4th term

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