99

I chose this problem because the answer is very clever.

There are 99 of you locked in one room. Everyone must choose a number between 1 and 100. You will only survive if no one else chooses the same number as you. Which one do you choose and why? Answered by Gaurav Gupta, Quora, July 20

Frankly, I'm going to assume we can't choose decimal numbers, as that would probably ruin this game and make it completely useless.
Next, I'll assume we have a limited amount of time to pick the number. This means that any coordination between the groups is impossible to achieve. So now I just have to guess, hoping no one chooses my number.

1. The first thing I'm going to do is ignore the spectrum (1-20) and (80-100), simply because most people will automatically turn to these numbers, leaving the numbers in the center relatively intact. We are left with more than spectrum 21 to 79. What to do now? Let me explain.

2. I will also eliminate the remaining numbers that could symbolize birthdays or a day of the month. So, spectrum 21 to 31. There is now a range of 32 to 79.

3. I will now forget all the even numbers because they are most likely to be caught because of the ease of division. Now here are the remaining numbers: 35; 37; 39; 41; 43; 45; 47; 49; 51; 53; 55; 57; 59; 61; 63; 65; 67; 69; 71; 73; 75; 77; 79.

4. I now remove the square numbers and then the numbers divisible by a digit (1 excluded). We then end up with this little list: 37; 41; 43; 47; 53; 59; 61; 67; 71; 73.
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5. I only have odd AND prime numbers left, very little used, so I am now one of those who have the best chance of winning. I choose …
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