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] = n^{2}

Sum of first n natural odd numbers is n^{2}

Mean of first n odd natural numbers = n^{2}/n = n

n = n^{2} /81

**n = 81**