GIVEN: First odd number is 1, second is 3, third is 5 and fourth is 7 FORMULA USED: an=a+(n−1)×d Sn=n/2[2a+(n−1)×d] 1Where n = number of terms, a = first term ,an=nth term, d = common difference, and Sn = sum of arithmetic progression CALCULATION:
a = 1 a2=3⇒a+d=3⇒1+d=3⇒d=2 Now, a198=a+197d=1+197×2=395