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Age 11 to 14
Challenge Level
Try some different numbers to get a feel for the problem.
Special numbers all satisfy the following equation:
$$a + b + ab = 10a + b$$
Special numbers all satisfy the following equation:
$$a + b + ab = 10a + b$$
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NRICH is part of the family of activities in the Millennium Mathematics Project.
NRICH is part of the family of activities in the Millennium Mathematics Project.