Here the sum of the series is 4+8+12+16+….. =612. find how many terms are there in the series?
Options: A) 15 B) 19 C) 17 D) 14 E) 13
Solution: This is an A.P. in which a=4, d=4 and Sn=612   Then, n/2[2a+(n-1)d]=612 =&gt; n/2[2*4+(n-1)*4]=612   =&gt; 4n/2(n+1)=612   =&gt; n(n+1)=306   =&gt; n^2+n-306=0   =&gt; n^2+18n-17n-306=0   =&gt; n(n+18)-17(n+18)=0   =&gt; (n+18)(n-17)=0   =&gt; n=17.   Number of terms=17.   Answer 17
<result>C</result>
Here the sum of the series is 4+8+12+16+….. =612. find how many terms are there in the series?