Question

which term of the AP:3,8,13,18,.......,is 78?​

Answer 1

Answer :

78 is the 16th term of given AP.

Explanation :

Given,

AP : 3, 8, 13, 18,...

$a_n$ = 78

In the given AP,

First term(a) = 3

common difference(d) = 8 - 3 = 5

According to the problem,

→ $a_n$ = a + (n - 1)d

→ 78 = 3 + (n - 1)5

→ 78 = 3 + 5n - 5

→ 78 + 5 - 3 = 5n

→ 80/5 = n

→ n = 16

Therefore,

$\boxed{n=16}$

78 is the 16th term of given AP.

Answer 2

Answer:

Answer :

78 is the 16th term of given AP.

Explanation :

Given,

AP : 3, 8, 13, 18,...

a_na

n

= 78

In the given AP,

First term(a) = 3

common difference(d) = 8 - 3 = 5

According to the problem,

→ a_na

n

= a + (n - 1)d

→ 78 = 3 + (n - 1)5

→ 78 = 3 + 5n - 5

→ 78 + 5 - 3 = 5n

→ 80/5 = n

→ n = 16

Therefore,

\boxed{n=16}

n=16

78 is the 16th term of given AP.