Philip received 75 points on a project for school. He can make changes and receive two-tenths of the missing points back. He can make corrections as many times as he wants. Create the formula for the sum of this geometric series and explain your steps in solving for the maximum grade Philip can receive. Identify this as converging or diverging.

  • The formula would be $$S_n= \frac{a_1-a_1r^n}{ 1-r}$$

    but am I missing something and how do I find $n$? Is it diverging?

  • $\begingroup$ Please formate the formula so that it is readable. :-) $\endgroup$ – BIS HD Oct 24 '13 at 1:45
  • $\begingroup$ how is that not readable? $\endgroup$ – sarah Oct 24 '13 at 1:45
  • $\begingroup$ Now it is ;) Thanks @Pocho la pant era $\endgroup$ – BIS HD Oct 24 '13 at 9:26


$$ S_n=a_1+a_1r+\cdots+a_1r^n $$ Then $$ r S_n +a_1=S_n+a_1r^{n+1} $$


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