Answers:
(i)
Given,
A.P is 7, 10, 13,…
a1 = a = 7
a2 = 10
Common difference, d = a2 – a1 = 10 – 7 = 3
an = a + (n – 1)d
an = 7 + (n – 1)3
= 7 + 3n – 3
= 3n + 4
Put, an = 68
3n + 4 = 68
3n = 68 – 4
3n = 64
n = 64/3
64/3 is not a natural number
68 is not a term of given A.P.
(ii)
Given,
A.P is 3, 8, 13,…
a1 = a = 3
a2 = 8
Common difference, d = a2 – a1 = 8 – 3 = 5
an = a + (n – 1)d
an = 3 + (n – 1)5
= 3 + 5n – 5
= 5n – 2
Put, an = 302
5n – 2 = 302
5n = 302 + 2
5n = 304
n = 304/5
304/5 is not a natural number
304 is not a term of the A.P.