I am a positive perfect square strictly less than 100. Subtract 1 from me, and the result is a multiple of 10. Divide me by 7, and I leave a remainder of 4. What number am I?
81
Square numbers under 100 ending in 1 (so subtracting 1 yields a multiple of 10) are 1 and 81. Testing 81: 81 / 7 = 11 with a remainder of 4 (77 + 4 = 81).
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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