Question 1145656
.
<pre>
It is arithmetic progression with the first term {{{a[1]}}}= 30,  the common difference d= 2  and the sum of the first n terms of 3950.


The formula for the sum of the first n terms is


    {{{S[n]}}} = {{{(a[1] + ((n-1)*d)/2)*n}}}


Substitute here  {{{S[n]}}} = 3950,  {{{a[1]}}} = 30  and d= 2. You will get


    3950 = {{{(30 + ((n-1)*2)/2)*n}}} = 30n + n*(n-1) = n^2 +29n


    n^2 + 29n - 3950 = 0

    n = {{{(-29 +- sqrt(29^2 + 4*3950))/2}}} = {{{(-29 +- sqrt(16641))/2}}} = {{{-29 +- 129)/2}}}.


Only positive value is meaningful  n = {{{(-29 + 129)/2}}} = {{{100/2}}} = 50.


<U>ANSWER</U>.  50 rows.    
</pre>

Solved.


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For introductory lessons on arithmetic progressions see 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Sequences-and-series/Arithmetic-progressions.lesson>Arithmetic progressions</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Sequences-and-series/The-proofs-of-the-formulas-for-arithmetic-progressions.lesson>The proofs of the formulas for arithmetic progressions</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Sequences-and-series/Problems-on-arithmetic-progressions.lesson>Problems on arithmetic progressions</A>  

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Sequences-and-series/Word-problems-on-arithmetic-progressions.lesson>Word problems on arithmetic progressions</A>

in this site.


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-II in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-II - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this online textbook under the topic <U>"Arithmetic progressions"</U>.



Save the link to this textbook together with its description


Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson


into your archive and use when it is needed.



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Comparing with the solution by @greenestamps, &nbsp;notice that I solved the problem algebraically 
and presented &nbsp;<U>THE METHOD</U> &nbsp;to you, &nbsp;while he simply &nbsp;"guessed" &nbsp;the answer.


The difference should be absolutely clear to you . . .