I am a single positive digit. Multiply me by any other single digit, and the sum of the digits of the resulting answer will always equal me. What number am I?
9
Any single-digit multiple of 9 (e.g., 9 × 2 = 18, 9 × 5 = 45, 9 × 8 = 72) has digits that add up to 9 (1 + 8 = 9, 4 + 5 = 9, 7 + 2 = 9).
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Easy. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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