Logic Puzzles

[llcoolvad]

I spent a tiny chunk of today not doing work and doing these instead: Some math/logic problems.

Ok, a couple were easy. I managed to answer 3, 4, 6, 7, 8, 9, 10, 11, 12 pretty easily. I was too lazy to do 13, because that was all math and I was tired by then. #1 I finally cheated on. #5 I got wrong -- and there's a huge argument on the answer page where some guy argues the way I would have if A. this hadn't already happened, and B. I was a lot smarter.

#2 I still don't understand. I have never been able to do probability-type logic problems. I like ones were I can draw them on paper (or today, in Powerpoint) and work them out.

And #14 is a cheat; my answer was to get a friend to stand upstairs, duh! But their answer is clever...and cheating!

Answers here, but try them first, they're fun!

Comments

[kicking-k.livejournal.com]

I didn't even understand the answer to 2, let alone how it works, so I'm glad I'm not alone. But I couldn't do 1, 9, 11, 12, 13 or 14 either. I knew I didn't deserve that B in Maths. I got 5, but that's because I've encountered it before (as the "Monty Hall goat problem").

However, I couldn't resist posting a comment to the "answers" thread:

"I'm not a mathematician, although I understand that the odds in the Monty Hall problem are 1/3.

But I was so hoping that someone would propose this alternative answer[to question 5], and nobody has, so here it is:

The odds of the second child being a daughter are nil, because if both her children were girls, she'd have said, "I have two daughters." Or "two girls". She wouldn't be likely to refer to her progeny as "children" unless she had one of each gender.

Hey, I think it's equally as mathematical as the answer to question 14!"

Does this make me a bad person?

[llcoolvad.livejournal.com]

Ha! That's good!

I guess the part I don't get about question 5 is if it's just a probability question that you ignore things like biology about, then why wouldn't it be just 50%? I mean, I get the GB, BB, GG, BG concept, but the question isn't which child is older or any of that, just what is the likelihood that the other child is a girl. So the only possibilities are GB and GG, right? 50/50. GB and BG are the same thing, for this question.

When you introduce Biology into the whole question, and I don't know this part for a fact, of course, but isn't it MORE likely that you'll have another girl if you already have one? I know a lot of people with multiple kids, and usually there is a whole lot more of one sex than the other. Assuming the fathers are the same. I had a friend in high school where there were six kids, only one boy. P has two brothers. My work friend has two boys. Another work friend has two girls, one boy. Wouldn't that part actually tilt the odds more? So I guess I completely disagree with 33%, but obviously I am no mathematician.

[kicking-k.livejournal.com]

I don't know much about biology, but my own family runs girl, girl, boy... (I'm the eldest.)

As I understand it, you're quite right about the age of the child that's present having no bearing on the other child's gender. But I'm no mathematician either. I have a slightly wonky brain that sometimes gets the right answer to mathematical problems without being able to do the working... (Yes, this is a cop-out.)

[ozymandiasism.livejournal.com]

I suck at these things. I think I got 1 or 2 questions right. I can't bare to sit and think about these things too long (unless I'm in a classroom and it's an actual test or soemthing). Ended up reading the answers a mintue after I read the questions.