The sum of all the two-digit odd numbers is

Sum of odd numbers $=\mathrm{n}^2$ Two-digit odd numbers are from $11-99$. Number of odd numbers from 1 to $99=50$ Sum of odd numbers from 1 to $99=50^2=2500$ Number of odd numbers from $1+9=5$ Sum of odd numbers from 1 to $9=5^2=25$ So, Sum of all two digit odd numbers $=2500-25=2475.$