How many children will have sent in the correct answer?

Answer

Dear Benito,
you can’t calculate that of course. That is precisely why such questions are often used as tie-breaker questions. You can sometimes reason a little. For example, suppose there is a competition in a magazine. Then you can check how many copies that magazine is printed on. Then you have to estimate how many of the readers think they will participate. Of course you have no idea, but you could bet on 20 percent. If the magazine is then printed in 100,000 copies, 20,000 people would participate. Even if you know how many people participated last time, you can approach that number again.
But of course it remains largely gambling. That is also the purpose of a tiebreaker: to ensure that no one has more chance than another, no matter how young or old, how smart, how rich… he is. That’s the most fair.