SOLUTION: Consider the arithmetic series 2+9+16+... . Find the number of terms that will give a partial sum of 335.

Question 1039328: Consider the arithmetic series 2+9+16+... . Find the number of terms that will give a partial sum of 335.
Answer by chen.aavaz(62) (Show Source): You can put this solution on YOUR website!
This is an arithmetic sequence with common difference d=(9-2)=7 (we subtract any two subsequent terms).
The nth term is calculated as follows:

The sum of the first n numbers is

In our case, Sn=335, a1=2 and d=7,
Therefore:
and by solving the quadratic equation we get n=10 (by keeping only the positive root).
So the answer is 10 terms.
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