Given, A.P. 7, 10, 13,…
Here, a = 7 and d = a2 – a1 = 10 – 7 = 3
We know that, nth term an = a + (n – 1)d
Required to check nth term an = 68
a + (n – 1)d = 68
7 + (n – 1)3 = 68
7 + 3n – 3 = 68
3n + 4 = 68
3n = 64
⇒ n = 64/3, which is not a whole number.
Therefore, 68 is not a term in the A.P.
