Question -
Answer -
Let a and b be thefirst and last terms
The series be a, A1,A2, A3, …….., An, b
We know, Mean =(a+b)/2
Mean of A1 andAn = (A1 + An)/2
A1 =a+d
An = a– d
So, AM = (a+d+b-d)/2
= (a+b)/2
AM between A2 andAn-1 = (a+2d+b-2d)/2
= (a+b)/2
Similarly, (a + b)/2is constant for all such numbers
Hence, AM = (a + b)/2