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Not everyone can solve it: a tricky math puzzle
Solving puzzles requires a sharp mind - it's a fact. And to solve math puzzles, you also need logic.
You can test yourself with the help of the problem published by OBOZ.UA today. Its condition is quite simple: you need to tell how many times the number 7 occurs between 1 and 100.
To help you better understand the essence of the task, let's formulate it a little differently. Imagine that you are a builder who is constructing a street of 100 houses. Now they are ready and you need to put numbers on them. How many 7s will you need to do this?
This task may seem simple. But for some reason, most people get it wrong. That's because they make the same mistake.
We are talking about those who say that a builder will need eleven signs, for those numbers that end with 7 - 7, 17, 27, 37, and so on.
However, these people forget that they also start with a seven.
Thus, you need a sign with a seven for houses with numbers 7, 17, 27, 37, 47, 57, 67, 70, 71, 72, 73, 74, 75, 76, 77 (two of them), 78, 79, 87, and 97. You can even count them manually - it makes 20. And this is the correct answer to the puzzle.
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