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Enigmas & puzzles

By Ian Stewart   September 2005


“This sudoku puzzle is really hard,” said Sanguimenta. “But I’m not giving up!”

“You could try trial and error,” suggested her sister Nonsequita. “How many different sudoku grids can there be, anyway?”

“Six sextillion, six hundred and seventy quintillion, nine hundred and three quadrillion, seven hundred and fifty-two trillion, twenty-one billion, seventy-two million, nine hundred and thirty-six thousand, nine hundred and sixty,” said Sanguimenta instantly.

“Oh. How do you know that?”

“It’s too complicated to explain.”

“Then try something simpler. What about a smaller grid?”

“It would have to be four by four, instead of nine by nine…”…

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