If the sum of the series 2+5+8+11+ ... is 60100, then the number of terms is

Let the number of terms be n Let S=2+5+8+ ... +  n  terms ∴            60100=n2[4+(n−1)3] ⇒        60100×2=3n2+n ⇒                    3n2+n−120200=0 ⇒     3n2+601n−600n−120200=0 ⇒      n(3n+601)−200(3n+601)=0 ⇒           (n−200)(3n+601)=0 ⇒                          n=200   (∵  n  cannot  be  negative)