I am a two-digit number. My tens digit is twice my units digit. If you subtract 27 from me, my digits flip. What number is this?
63
Let the number be 10t + u. We know t = 2u and (10t + u) - 27 = 10u + t. Substitute t = 2u: (20u + u) - 27 = 10u + 2u, which simplifies to 21u - 27 = 12u, leading to 9u = 27, so u = 3 and t = 6.
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: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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