If are in A.P, then possible value of n is
6
12
14
21
As we learnt in
Arithmetic mean of two numbers (AM) -
- wherein
It is to be noted that the sequence a, A, b, is in AP where, a and b are the two numbers.
Option 1)
6
Incorrect
Option 2)
12
Incorrect
Option 3)
14
Correct
Option 4)
21
Incorrect