Brain Teaser Answers.
1. Don’t overthink this. Each baby born is as equally likely to be a boy as a girl. Therefore, the ratio of girls to boys must be 1:1. It’s as simple as that.
2. The most straightforward approach would be to break a link on the end of each of the five chains, and then reattach the link to the back of the next chain in the loop. This would cost you $50 for the five links that were broken and resealed. To do it for $40, Instead of breaking a link in each chain, break all four links in one of the 5 four link chains and then use those four links to attach the remaining four chains together. Now you’ve saved $10. Spend
it on something nice.
3. Suppose the spoon was the same size as the entire glass. In that case, putting Alan’s “spoonful” of whisky into Claire’s water would entail mixing both glasses together, leading to a mixture that’s half water and half whisky. Then, when Claire returns a “spoonful” of this mixture to Alan’s glass, there would be exactly half water and half whisky in both glasses.So in this extreme, there would be the same amount of water in Alan’s whisky as there is whisky in Claire’s water. Indeed, this is the solution no matter the size of the spoon.
4. 98 - 76 + 54 + 3 + 21 equals 100. (3 plus and 1 minus).
5. To figure this out, let’s go back to what Jaya initially observes: She sees Julian has 20 on his forehead and Levi has 30 on his. That means she can either be 50 (their sum), or 10 (their difference). Let’s suppose Jaya were 10. Then Julian would have seen 10 (on Jaya) and 30 (on Levi), thus thinking he was either 20 or 40, and would say he doesn’t know what number he is. Now it comes to Levi, who would see 10 on Jaya and 20 on Julian. He would think, then, he’s either 10 (the difference) or 30 (the sum). But wait! Levi can’t be 10, because Cecilia told everyone all three numbers are different from one another, and Jaya is already 10. So Levi would know he was 30, and would say so. Since he said he didn’t know his number, Jaya can’t be 10. Thus, she knows she’s 50.