Results 1 to 3 of 3

Thread: Geometric progression formula confusion with 100(1.01)(1.01n-1/1.01-1)

  1. #1

    Geometric progression formula confusion with 100(1.01)(1.01n-1/1.01-1)

    Morning/afternoon/evening all,

    I'm aware of the formula: a(rn-1/r-1).

    However, for the following:

    100(1.01)(1.01n-1/1.01-1)

    Apparently (Mathematics for Economics and Business - Ian Jacques), this is the same as:

    10,100(1.01n-1)

    Is that correct? I can't find out how to get to this.

    Your help is always appreciated.

  2. #2
    Full Member
    Join Date
    Nov 2017
    Location
    Rochester, NY
    Posts
    870
    Quote Originally Posted by radnorgardens View Post
    Morning/afternoon/evening all,

    I'm aware of the formula: a(rn-1)/(r-1).

    However, for the following:

    100(1.01)(1.01n-1)/(1.01-1)

    Apparently (Mathematics for Economics and Business - Ian Jacques), this is the same as:

    10,100(1.01n-1)

    Is that correct? I can't find out how to get to this.

    Your help is always appreciated.
    I added parentheses that are needed to make this mean what you intended.

    Here is how you get the simplified form:

    100(1.01)(1.01n-1)/(1.01-1) = 101 (1.01n-1)/(0.01) = 101/0.01 (1.01n-1) = 10100 (1.01n-1)

    Follow that? (100)(1.01) = 101, and dividing by 0.01 multiplies by 100.

  3. #3
    Quote Originally Posted by Dr.Peterson View Post
    I added parentheses that are needed to make this mean what you intended.

    Here is how you get the simplified form:

    100(1.01)(1.01n-1)/(1.01-1) = 101 (1.01n-1)/(0.01) = 101/0.01 (1.01n-1) = 10100 (1.01n-1)

    Follow that? (100)(1.01) = 101, and dividing by 0.01 multiplies by 100.
    Ah right. Because when I expand it out:
    101 x (1.01n-1) / 0.01

    Then rearrange to:
    101 / 0.01 x (1.01n-1)

    Becomes:
    10100 x (1.01n-1) i.e. 10100 (1.01n-1)

    Great - thank you Dr.Peterson.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •