Question

which term of an A.P. 3,8,13,18,.........IS 78

Answer 1

here the first term a=3
common difference d=5
nth term of the ap (an)=78
an=a+(n-1)d
78=3+(n-1)5
75/5=n-1
15+1=n
16=n
therefore 16th term of ap is 78

Answer 2

Here first term (a) = 3

common difference (d) = 5

an = 78

a + (n-1)d = 78

3 + (n-1)(5) = 78

5n - 5 = 75

5n = 80

n = 80/5

n = 16

This is 16th term of this AP