Find the number of terms in the following A.P. 7, 13, 19,....,205
Let a,d and l be the first term, common difference and the last term of the A.P. respectively.
Given
a=7,d=13−7=6 and
l=205Since l=a+(n−1)d
⇒205=7+(n−1)6
⇒198=(n−1)6
⇒33=n−1
⇒n=34
Hence, there are 34 terms in the A.P.