The n^th term of the A.P. 6, 11, 16, 21, ……. is 106, the the value of n - 4 is :

1. 17

2. 15

3. 16

4. 20

In A.P.,

6, 11, 16, 21, ……..

First term (a) = 6,

Common difference (d) = 11 - 6 = 5.

nth term (a_n) = 106

By formula,

⇒ a_n = a + (n - 1)d

⇒ 106 = 6 + (n - 1)5

⇒ 106 = 6 + 5n - 5

⇒ 106 = 5n + 1

⇒ 106 - 1 = 5n

⇒ 5n = 105

⇒ n = $\dfrac{105}{5}$ = 21.

⇒ n - 4 = 21 - 4 = 17.

Hence, Option 1 is the correct option.