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It's All in the Numbers: BGP's Thread of Math Problems, Puzzles, Teasers, Fun&Games!


Science Friction

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One of my oldies but goodies.

 

Eccentric old Professor Friction is running late for school. After hurriedly combing his seven hairs and brushing his tooth, he opens his dresser and reaches in to get a sock. After getting one, he pulls out a second sock. The room is pitch dark so he can't tell what color the socks are. Also, all the socks are made identically, so he can't tell which is which just by feel. And of course, Prof. SF is very unorganized so the socks are just randomly scattered about in the drawer.

 

Suppose the socks are one of two colors, red or green. Also, there are 6 total socks in the drawer. If there is a 2/3 probability of his choosing two red socks, what is the probability that he goes to school wearing two GREEN socks?

 

Very quickly done, but I believe the chances of two green socks is 0%.

 

If RR =.66, that should indicate that there are 5 red and only 1 green socks in the 6....5/6 (83%) x 4/5 (.80) = .66% of RR.

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Yes sir... that is indeed the quick response. Question is, why is that not the correct response. :) If there were no prior "knowledge" about the sex of the children, the answer is 1/8. But, given the condition that at least one of the children will be a boy(that is, at least one boy is guaranteed), what's the likelihood of all three being boys? So, three girls is not an option.

 

1/4 or 25%....100% x 50% x 50% = 25%

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Very quickly done, but I believe the chances of two green socks is 0%.

 

If RR =.66, that should indicate that there are 5 red and only 1 green socks in the 6....5/6 (83%) x 4/5 (.80) = .66% of RR.

 

I knew I liked you for some reason!!! Now I know why; you're awesome with probability teasers !!! :)

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Here is a relatively simple one that I've seen people shout at each other over it because they disagree.

 

23031637_1496101567093636_1627508473837419651_n.jpg?oh=298a2a08dfcdb392191add8f61833d86&oe=5A67E9E8

 

D

 

She stole $100, then received $70 worth of groceries, which she paid for with the stolen money. (still puts her up $100)

 

She gets $30 in change.

 

Stole $130 in cash and prizes total.

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Here is a relatively simple one that I've seen people shout at each other over it because they disagree.

 

23031637_1496101567093636_1627508473837419651_n.jpg?oh=298a2a08dfcdb392191add8f61833d86&oe=5A67E9E8

 

I'll go with "C"...

 

Store owner has her $100 bill back, and is out $70 in goods + $30 that she gave back in change. Owner is out $100 after all said and done.

 

Obviously we don't know the mark-up from the owner's original purchase of the sold items, so going solely on what we do know, this would have to be the answer.

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C...

 

D

 

She stole $100, then received $70 worth of groceries, which she paid for with the stolen money. (still puts her up $100)

 

She gets $30 in change.

 

Stole $130 in cash and prizes total.

 

I'll go with "C"...

 

Store owner has her $100 bill back, and is out $70 in goods + $30 that she gave back in change. Owner is out $100 after all said and done.

 

Obviously we don't know the mark-up from the owner's original purchase of the sold items, so going solely on what we do know, this would have to be the answer.

 

It is C $100, but like I said I've seen so many people argue over this that it's not funny.

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I gave it a whirl from a non math perspective looking at time zones and bordering countries...like UKMustangFan I'm regrettably clueless also.

Maybe with a small hint or clue, but right now I'm stuck also.

 

It's a toughie. Just Jim nailed it. I think what makes it challenging is that most folks go in the geography direction, which is certainly a logical starting point. I really appreciate you pondering the teaser, though. Also, thanks for adding to the thread. Keep 'em coming. I love working them as well.

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