the mean of first n odd natural numbers is n2/81,then n=

Sum = 1 + 3 + 5 + 7 + ............ 2n - 1

This forms an AP with first term = 1, common difference = 2

Sum of first n terms of the AP = n/2[2x1 + (n-1)x2]

Sum = n/2[2 + 2n - 2] = n²

Sum of first n natural odd numbers is n²

Mean of first n odd natural numbers = n²/n = n

n = n² /81

n = 81