I love logic puzzles, and a friend showed me some particularly good ones the other day. These are based on puzzles written by the Mathematician from AskAMathematician.com.
If you’re the first to get all three of them correct with correct explanations for all of your answers, you’ll win a prize! Skepticon will send you either 4 Skepticon pint glasses or 6 Skepticon shot glasses. To be eligible for the prize, include the work “banana” in your comment.

And as a bonus just for fun – these questions were from a larger set of 8, and I included the only question I got wrong. Which one did I mess up on?

Question 1: In front of you are four cards. You know that each card has a photo of a famous person on one side, and a photo of an animal on the other. The four sides that are visible to you are as follows: Ken Ham, Richard Dawkins, a narwhal, and a T-Rex. I let you know that all of these cards follow the same rule – that if a card has a religious person on it’s famous person side, it has a dinosaur on its animal side. What’s the lowest number of cards you’d need to flip to determine if this rule is true or false for these cards, and which cards would you flip?

Question 2: Because I’m super nice, I give you a giant one hundred pound watermelon as a gift. You determine that this giant watermelon is ninety-nine percent water by weight. Unfortunately you let the watermelon sit out in the sun, and some water evaporates. Now the watermelon is only ninety-eight percent water by weight. To the nearest pound, what does the watermelon now weigh?

Question 3: While you were at TAM9, you decided to suspend skepticism and gamble – specifically, by playing roulette (you can actually go and play roulette online if you like the game of odds, even if you were to do something like play cards online in Vietnam there can be a large number of roulette games offered). But since you want to have some sort of strategy, you decide to flip a coin before each bet to decide whether to place a bet on red or on black (which should have a 50/50 chance of happening). Sadly, you lose sixty seven times in a row – that is, the ball always lands on the opposite color that you pick. That’s bad luck, pure and simple – it would be unfortunate if this were to happen to you when playing roulette online but hopefully you’ll have more luck on your side when you check out the games over on this website where there are plenty of games to try your hand at, even if roulette’s not your thing. If you turned your skepticism back on, it would be most rational to think:

A. You just have bad luck
B. It’s terrible strategy to flip a coin to pick what color to bet on in roulette
C. You should keep up this strategy because you’ve really likely to win the next bet
D. The roulette table is obviously broken, but you can’t assume that’s intentional
E. The casino or the staff are dirty crooks who have rigged the game against you somehow
F. You can’t reasonably decide which of the listed options are more likely

Good luck!

EDIT: Katie from Skepticon adds:

“Keep posting! Even if someone has already given your response, I’m strongly considering a small consolation prize (for the first 10 correct folks), so it’s in your best interest to post. Unless you don’t like getting special prezzies in the mail, of course. :)”

This is post 10 of 49 of Blogathon. Pledge a donation to the Secular Student Alliance here.