The series of positive multiples of 3 is divided into sets: $\{ 3 \} , \{ 6,9,12 \} , \{ 15,18,21,24,27 \} , \ldots$ Then the sum of the elements in the $11 ^ { \text {th} }$ set is equal to $\_\_\_\_$.
The series of positive multiples of 3 is divided into sets: $\{ 3 \} , \{ 6,9,12 \} , \{ 15,18,21,24,27 \} , \ldots$ Then the sum of the elements in the $11 ^ { \text {th} }$ set is equal to $\_\_\_\_$.