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March 30, 2017

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A child organizes animal blocks in rows on the ground. There are 64 animal blocks in the 5th row & 92 of those blocks in the 9th and last row. Suppose that the number of animal blocks frm row to row form an arithmetic sequence.

The number of animal blocks in the first row is....

I can’t seem to find a pattern, having a hard time solving this problem too.
Also How do I find the total number of blocks used in the arrangement?

The answer somehow is 36, and the total number of blocks is 576. I don't know how to get this.

Im probably supposed to use one of these formulas... Sn = n[2a +(n-1)d]/2
Sn = n(a +tn)/2. Still I don't get how to do it

  • Math Block Problem - ,

    the difference between the ninth and fifth is 28, so that is between 4 rows, so the differnce between each row is 28/4=7

    start with 9th and go down:

    92
    85
    78
    71
    64
    57
    50
    43
    36 first row.

    Sum them: Sn= 9(2*36+8*7)/2=9*(72+56)/2=
    Sn=9*64=576

  • Math Block Problem - ,

    Thanks so much. I was so confused :)

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