If the mean of the set of numbers x1,x2,x3,…,xn is x¯, then the mean of the numbers xi+2i,1≤i≤n is
x¯+2n
x¯+n+1
x¯+2
x¯+n
We know that x¯=∑i=1n xin
⇒ ∑i=1n xi=nx¯∴ ∑i=1n xi+2in=∑i=1n xi+2∑i=1n in=nx¯+2(1+2+…n)n =nx¯+2n(n+1)2n=x¯+(n+1)