Question

if the mean of first n terms of AP 2,5,8..... is 17,the value of n is?​

Answer 1

In an AP,

17=2+5+8+.........+n/n

17n=2+5+8+.......+n

there fore,Sn=n/2{2a+(n-1)d}

17n=n/2{2×2+(n-1)3}

17×2=4+3n-3

34=1+3n

34-1=3n

33=3n

11=n