Question

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

Answer 1

Answer for this question is 16

Answer 2

Answer!

This is an AP. nth term of AP is given by a + ( n - 1 )d, where symbols have their usual meanings.

Here,

a = first term = 3

d = comm. diff. = 8 - 3 = 5

Let the required number of terms be n.

⇒ 78 = 3 + ( n - 1 )5

⇒ 78 - 3 = ( n - 1 )5

⇒ 75 = ( n - 1 ) 5

⇒ 75/5 = 15 = n - 1

⇒ 15 + 1 = n

⇒ 16 = n

Hence the required number of terms is 16