Question

Which term is 78: when A.p=5,8,13,18-----

Answer 1

here
a = 5
d= 3
an = 78
n= ?
an = a+ ( n- 1) d
78 = 5 + ( n-1)3
78 - 5 = ( n- 1) 3
73/3 = n-1
n = 73 / 3 + 1
= 76 / 3
n can be in the form p/ q
so no term of this AP will be 78

Answer 2

An =78
a=5
d=3
An=a+(n-1)d
78=5+(n-1)3
78-5=(n-1)3
73=(n-1)3

73/3=(n-1)
n=25.3

No term is 78 ..

or Question might be wrong...