A book has pages numbered from 1 to 100. How many times does the digit '7' appear across all page numbers?
20 times
The digit 7 appears in the ones place 10 times (7, 17, 27, 37, 47, 57, 67, 77, 87, 97) and in the tens place 10 times (70, 71, 72, 73, 74, 75, 76, 77, 78, 79). Combined, it appears 10 + 10 = 20 times.
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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