Results 1 to 2 of 2

Math Help - Tricky sequences and series question

  1. #1
    Junior Member
    Joined
    Nov 2007
    Posts
    52

    Tricky sequences and series question

    A timber worker is stacking logs. the logs are stacked in layers, where each layer contains one log less than the layer below. There are five logs in the top layer, six logs in the next layer and so on. There are n layers altogether.

    a. Write down the number of logs in the bottom layer

    b. Show that there are \frac{1}{2} n(n+9) logs in the stack
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Nov 2008
    Posts
    6
    a) There are a+(n-1)d logs in the nth layer, with 'a' referring to the first number in the sequence (5) and 'd' referring to the common difference (1). n refers to the layer which you are looking at.

    5+(n-1)1 = 5+n-1 = n+4

    to prove > we know the third layer will have 7 logs in. 3+4 = 7

    b) Here you must use the equation for finding the sum of the terms in an arithmetic sequence.

    a=5
    d=1
    n=?
    Sn=?

    Sn=1/2n [2a + (n-1)d]
    Sn=1/2n [10 + (n-1)1]
    Sn=1/2n [10 + n - 1]
    Sn=1/2n [n + 9]

    There she blows
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Sequences and series question.
    Posted in the Calculus Forum
    Replies: 4
    Last Post: October 11th 2010, 07:47 AM
  2. series and sequences question
    Posted in the Algebra Forum
    Replies: 1
    Last Post: September 24th 2008, 11:11 AM
  3. Sequences and Series - Power Series Question
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 20th 2008, 07:32 PM
  4. Another Question regarding Sequences and Series
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: September 10th 2007, 10:13 AM
  5. Sequences/Series question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 1st 2005, 12:39 PM

Search Tags


/mathhelpforum @mathhelpforum