If said this one before: If a brick ways 7lbs plus half a brick, how much does a brick and a half weigh?
Spoiler going with 7lbs (known) and additional 1/2 brick (another 7lbs) = 1 brick total is 14lbs (7lbs plus 1/2 of total brick) thus another 7lbs : so brick and 1/2 of a brick weighs 14 + 7 = 21 lbs)
Spoiler 7 pounds... algebra... let x = weight of brick, we know x = 7 + 1/2(x), therefore 1/2(x) = 7 and also x = 14
this one is a classic math one for all you math geeks Three guests check into a hotel room. The clerk says the bill is $30, so each guest pays $10. Later the clerk realizes the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn't know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 for himself. Now that each of the guests has been given $1 back, each has paid $9, bringing the total paid to $27. The bellhop has $2. If the guests originally handed over $30, what happened to the remaining $1?
Spoiler Obama took it and claims he will be sharing the wealth always one of my favorite crazy ones...
oh I see what I did wrong... I solved it for half a brick. See... the words get in the way of the math
If you really want to mess with someone, preferably a small child... try this one: take a piece of paper and draw three houses (nothing fancy, it can be just a triangle), then draw three utlilty stations (electricity, gas and water for example) you can use a square as opposed to a rectangle. Now, you are the city planner, you need to design a way for each house to receive one of each utility. The CATCH is that the lines that you draw CANNOT cross no matter what! Give it a try, the lines can curl around, they do not have to be straight lines but must be continuous... Read this spoiler only after you've tried it and are completely frustrated that you can't get the answer... I mean to the point of tears!!! Spoiler so you want the answer? Well, there is no answer. It cannot be solved. You know you love me....
Spoiler Actually it can. If you're using a real world example then saying the lines can go under and over each other considering there's a third dimension and everything. So I'd say skip the real world scenario and tell the kid draw 3 lines from each circle to each triangle and they can't cross.
You have 9 coins. One of the 9 coins is counterfeit, the counterfeit coin can only be distinguished by weight (it's heavier than the rest). Using a balance scale only twice, find the counterfeit coin.
8 plus 8 is 16... you only have 9 coins... Spoiler I'm actually not sure how to solve this one... you can only use the scale twice. If you put four on each side and you're in balance, then as lmeister says, the one left out is the counterfeit. But if you are unbalanced, you can split the heavier side into a two by two scale measurement. One side would be heavier again, but there is no way to distinguis between the remaining two coins without weighing them and thus using the scale for a third time. this is a good one... I suppose it has something to do with adding the ninth coin from the first measurement back into the population
Spoiler You could do all of that, and then take the two coins from the heavy side and... Put them on a non balance scale or drop them in water and see which one sinks fastest. etc. That's my problem with some teasers, is that they can have multiple answers that don't violate the premise so they aren't technically wrong. And you don't always know if that's the answer they are looking for, because some teasers play on that fact. Like the dead guy in the desert one. I mean, once you have 2 and 2 on the scale, does removing one from each side count as a third use of the scale?
Spoiler You weigh 3 vs 3 coins on the scale. If the counterfeit is in there, one side will be heavier. Take those 3, and pick any 2 and weigh them against each other. If one is heavier it will be obvious, if they are the same you know it's the unweighed one. If during the original 3 vs 3 measurement they were even, you know its one of the 3 unweighed ones, and you just do the same of picking 2 out of the 3 to weigh against each other
Spoiler re-read my post, i never said anything about a 3 vs 2 measurement On the initial 3 vs 3 measurement, if one side is heavier you take those 3 coins and those 3 only.. discard everything else. Of those 3 coins you know 1 has to be counterfeit, so keep 1 to the side, doesn't matter which, and weigh the other 2 1 vs 1. if they are even, its the one you kept to the side, if one is heavier, that's the counterfeit one
:P This is a most unusual paragraph. How quickly can you find out what is so unusual about it? It looks so ordinary you'd think nothing was wrong with it and in fact, nothing is wrong with it. It is unusual though. Why? Study it, think about it, and you may find out. If you work at it for a bit it will dawn on you. So jump to it and try your skill at figuring it out. Good luck! Also, I'm adding this part too just to say that Finascious D is a doofus, but it's okay, it's only adding humor, and shouldn't modify your solution to it at all.
There are hundreds of riddles on You Tube under Cool Riddles. Some of them are rubbish others are brilliant. If I give you the link it saves me typing some out http://www.youtube.com/user/CoolRiddles
I was thinking about the coin one this morning when I woke up. And solved it a few minutes later. Liked that one DarkKnight... you have to go to the advanced screen to use the spoiler tag (instead of quick reply). The spoiler tag is the last icon above where you type (black square with word spoiler inside). Just like quoting something, it works the same way.
Or without going to advanced screen, you can manually type the Spoiler blah, blah, blah [ Spoiler \Spoiler] just use / vs \ and it will be done! Just like /Quote is used when quoting something!
