126. Summation of numbers. Professor Rackbrain would like to know the sum of all numbers that can be formed from nine digits (0 is excluded), using each digit in each number only once.

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126. This problem can be solved in several ways. The answer, of course, is the same in all cases, equal to 201599999798400. The sum of nine digits is 45 and

\[
45 \times 8!=1814400
\]

Writing further

\[
18144
\]

18144

18144

18144 \( \qquad \)
nine times, adding them up and appending 00 at the end, we get the answer.

\(\rightleftarrows \rightleftarrows \rightleftarrows \rightleftarrows\)