What is your magic number? i.e. How many people have you had sex with? Is that public or private information? I would say that it is 100% private information. A question that really shouldn't be asked because 1) you don't REALLY want to know and 2) the answer you get will probably be a lie.

You do not want to know. For the ladies, if you ask a guy his magic number and it's too high, that might lead you to fall back. But on the other hand if it's real low, you might think he's a loser. For the fellas, you don't want to know because if it's too high, she's a hoe and if it's too low then she's lying. This is a lose/lose situation.

But if you still want to know, despite the reasons you shouldn't, there are methods of getting a number that you can be sure is close to the truth, if not the actual number. I will first start with how to get a man's magic number.

A Man's Magic Number:
Method 1 - Ask him. When you ask him he'll say X. Now take X and multiply it by 3, lets call that number N. His magic number is N + or - C. C is your confidence score, a number from 0-9. If you think N is too low then add C to N to get the magic number but if you think N is too high then subtract C from N to get the magic number. This may be confusing so let's do an example:

You ask him his number and he says 5. Take 5 and multiply it by 3, which is 15. If you think his real number is greater than 15 then you would add C. Now choose an estimate of C that would represent how much greater you think it is, lets say 5. So his magic number is 15 + 5 which is 20. Cool right? For all you mathematical people out there the equation is:
M = 3X +- C

Method 2 - Lets say you ask him and he doesn't give an answer. No problem. His magic number is his age + or - C. Once again, for anyone who cant keep up, I'll go through an example:

Lets say he's 25, his magic number is 25 + or - C. This time we'll choose C to be 7 and we think the guy doesn't look like he hit 25 chicks off so you subtract it from 25 to get 18. That's his magic number. This equation is:
M = A +- C

Now let's continue on to the ladies...

A Lady's Magic Number:
Method 1 - Ask her. She'll say X. Her real number is X + or - C. C is, once again, your confidence score for her but this time its a number between 1-3. I don't think I need to go through an example because guys are better at math than girls are... (just kidding;) The equation is:
M = X +- C

Method 2 - If she doesn't give an answer, take her age, A, and subtract it from 16 to get Y. Now take Y and multiply it by 3 to get N. Not take N and divide it by C, your confidence score. I'll go through an example because this one is a little tricky.

If a female is 20 then subtract that by 16 to get 4. Now take 4 and multiply it by 3 to get 12. Let's say you give a confidence score of 2 then her magic number is ~6. The equation for this is
M = (3*(A-16))/C

I know the equation for the ladies look more complicated and that is because females are more complicated.

I've tested my equations against 100% of the data not collected and each time I was within 1 or 2 of the actual number. I would say about 60% of the time, it works every time. I, personally, would not want to know but if you must my methods above are great ways to find out...