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# Riddle and Puzzle Thread

Post a riddle, let others solve it.

DO NOT USE A SEARCH ENGINE TO FIND THE ANSWERS. Don't ask other people, etc. If you can't figure it out, tough. If a riddle lasts a few days and hasn't been answered, the OP of the riddle should provide the answer.

Here's the first one. A classic.

You're standing at the bottom of the stairs. There are three light switches, one of which turns on a light in a bedroom with a shut door (no light can shine beneath or around the door) on the second floor. Without going down any stairs, how can you determine which switch controls the light bulb in that bedroom?

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Hmmm, I thought I had it, was about to excitedly, and smart-alec-ly respond with the answer, and then I realized I didn't.  So, just, hmmm ...

Quote:
Originally Posted by iacas

Post a riddle, let others solve it.

DO NOT USE A SEARCH ENGINE TO FIND THE ANSWERS. Don't ask other people, etc. If you can't figure it out, tough. If a riddle lasts a few days and hasn't been answered, the OP of the riddle should provide the answer.

Here's the first one. A classic.

You're standing at the bottom of the stairs. There are three light switches, one of which turns on a light in a bedroom with a shut door (no light can shine beneath or around the door) on the second floor. Without going down any stairs, how can you determine which switch controls the light bulb in that bedroom?

I thought this might be something akin to the old Monty Hall puzzle but that's to do with probabilities so it's not.

I reckon if you have 3 switches you turn on 1 + 2 and wait 5 mins. Then you turn off 2 leaving only 1 "on" you then go up the stairs (your puzzle says only that going "down" stairs isn't possible) to the room. If the light is on you know it's switch 1. If the light is off you know it's 2 or 3. If the bulb is warm you know it's 2 and if it's cold you know it's 3?

Afraid I don't know any to challenge with though. :/

Wait ... I got it!!!

The doctor is their mother!!!

Are we supposed to post our answers or just keep them to ourselves?

Quote:
Originally Posted by billchao

Are we supposed to post our answers or just keep them to ourselves?

Post. Then post a new riddle.
Quote:
Originally Posted by iacas

You're standing at the bottom of the stairs. There are three light switches, one of which turns on a light in a bedroom with a shut door (no light can shine beneath or around the door) on the second floor. Without going down any stairs, how can you determine which switch controls the light bulb in that bedroom?

I'm probably taking too many liberties with the parameters of the riddle: My solution is that you're standing on the second floor, at the bottom of the stairs to the third floor. Then all you'd have to do is open the bedroom door and test the switches, one by one, never having to go down a single step. You never mentioned specifically that you were on a different floor than the bedroom.

Here's one of my favorites:

You're in a maze and you've almost made your way to the end. Before you stand two guards, each one standing in front of a door. One of the doors is the way out; the other door leads to certain doom. One of the guards can only speak the truth and the other can only lie. You may ask one question of only one guard. How do you know which door to exit?

@billchao this was the answer:

Quote:
Originally Posted by MiniBlueDragon

I reckon if you have 3 switches you turn on 1 + 2 and wait 5 mins. Then you turn off 2 leaving only 1 "on" you then go up the stairs (your puzzle says only that going "down" stairs isn't possible) to the room. If the light is on you know it's switch 1. If the light is off you know it's 2 or 3. If the bulb is warm you know it's 2 and if it's cold you know it's 3?

Quote:
Originally Posted by billchao

You're in a maze and you've almost made your way to the end. Before you stand two guards, each one standing in front of a door. One of the doors is the way out; the other door leads to certain doom. One of the guards can only speak the truth and the other can only lie. You may ask one question of only one guard. How do you know which door to exit?

Those come in many forms. The answer is that you ask one guard (either one) what the other one would tell you to do. If it's the truthful guard, he'll say the lie. If it's the lying guard, he'll also say the lie. So you choose the opposite door.

Here's an easy one.

Two identical human boys were born to the same mother at the same time, yet they're not twins. How?

What type of tree has every vowel in it's name?

Quote:
Originally Posted by iacas

Post a riddle, let others solve it.

DO NOT USE A SEARCH ENGINE TO FIND THE ANSWERS. Don't ask other people, etc. If you can't figure it out, tough. If a riddle lasts a few days and hasn't been answered, the OP of the riddle should provide the answer.

Here's the first one. A classic.

You're standing at the bottom of the stairs. There are three light switches, one of which turns on a light in a bedroom with a shut door (no light can shine beneath or around the door) on the second floor. Without going down any stairs, how can you determine which switch controls the light bulb in that bedroom?

Reminds me of the Stephen Wright joke about a switch in his house that didn't seem to do anything.  He kept flipping it up and down.  Finally, a month later, a lady called from Germany and said, "Cut it out."

Quote:
Originally Posted by flopster

What type of tree has every vowel in it's name?

Sequoia. But you're supposed to answer the previous riddle before posting new ones:

Quote:
Originally Posted by iacas

Here's an easy one.

Two identical human boys were born to the same mother at the same time, yet they're not twins. How?

Quote:
Originally Posted by iacas

Two identical human boys were born to the same mother at the same time, yet they're not twins. How?

they were 2 of a set of triplets

you have three bags of marbles and you know:

1 bag is full of black marbles only

1 bag is full of white marbles only

1 bag is mixed black and white marbles

you know all three are each incorrectly marked with labels:  "white", "black", "mixed"

what is the minimum number of marbles you can withdraw from the bags needed for you to label them correctly

explain why

(hint - let's assume each bag holds 10 marbles each, though it doesn't matter how many really)

Quote:
Originally Posted by rehmwa

you have three bags of marbles and you know:

1 bag is full of black marbles only

1 bag is full of white marbles only

1 bag is mixed black and white marbles

you know all three are each incorrectly marked with labels:  "white", "black", "mixed"

what is the minimum number of marbles you can withdraw from the bags needed for you to label them correctly

explain why

(hint - let's assume each bag holds 10 marbles each, though it doesn't matter how many really)

One marble!!!

If you know that they are all incorrectly marked, then you start with the bag labeled "mixed."  Let's say you pull out a white marble.  Now you know that that bag HAS to contain only the white marbles.  You also know that the "black" labeled bag cannot be black, therefore it has to be "mixed" and that leaves the "white" bag with the black marbles.

Speaking of marbles ...

Let's say you have 9 marbles of the exact same size and shape, however, one is slightly heavier than the rest.  Using only a (balance) scale, and using it only 2 times, how do you determine which is the heavier ball?

Quote:
Originally Posted by Golfingdad

Let's say you have 9 marbles of the exact same size and shape, however, one is slightly heavier than the rest.  Using only a (balance) scale, and using it only 2 times, how do you determine which is the heavier ball?

I know this one, but I'll sit out for someone else as I don't have the next riddle or logic puzzle handy right here.

Quote:
Originally Posted by rehmwa

Quote:
Originally Posted by iacas

Two identical human boys were born to the same mother at the same time, yet they're not twins. How?

they were 2 of a set of triplets

you have three bags of marbles and you know:

1 bag is full of black marbles only

1 bag is full of white marbles only

1 bag is mixed black and white marbles

you know all three are each incorrectly marked with labels:  "white", "black", "mixed"

what is the minimum number of marbles you can withdraw from the bags needed for you to label them correctly

explain why

(hint - let's assume each bag holds 10 marbles each, though it doesn't matter how many really)

If you already know, why is it hard to tell? If not, then are the bags clear or opaque?

Quote:
Originally Posted by Lihu

If you already know, why is it hard to tell? If not, then are the bags clear or opaque?

it's a logic puzzle - it's a defined part of the problem.  Don't overthink it.

If you, sigh, want to wordsmith it, then change "know" to "you are informed that"

Quote:
Originally Posted by Golfingdad
Let's say you have 9 marbles of the exact same size and shape, however, one is slightly heavier than the rest.  Using only a (balance) scale, and using it only 2 times, how do you determine which is the heavier ball?

3 on one side of the scale, 3 on the other, 3 off on the table

take the 3 heavy ones (if the scale balances, use the 3 from the table)

now

1 on each side of the scale and 1 one the table - same logic to pick the heaviest....

Next:  (I know, still a puzzle, not a riddle)

Jack went to the store to sell corn and peas. He only had one bag and needed to keep them separate, so he put the corn in first and tied the bag over the corn, then he put the peas in the bag above the knot.   A buyer for the corn came by with his own bag.  He did not want the peas.

How do we pour the corn into the buyers sack?

Constraints - Pouring the content anywhere else but the sacks is considered soiling.  You can't soil the peas. The buyer wants to keep his own bag.  Jack needs to keep the peas in his own bag. You can't cut a hole in either bag.  (they are very big and loose bags)

Quote:
Originally Posted by Golfingdad

Let's say you have 9 marbles of the exact same size and shape, however, one is slightly heavier than the rest.  Using only a (balance) scale, and using it only 2 times, how do you determine which is the heavier ball?

Not sure if it's been answered, but didn't want to scroll through and ruin possible answers to other riddles!

Randomly separate the balls into three groups of three, say groups A, B, and C.  Compare groups A and B on the balance scale.  If they weigh the same, then the heavier ball is in group C.  Otherwise, you the heavier group of three contains the heavier ball.  Say the group with the heavier ball is group A.  Now choose two balls randomly from group A.  Compare them on the balance scale.  Either one is heavier than the other and you've found the heavier ball, or they weigh the same, and the heavier ball is the one ball you left out.

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New Riddle:

You are given 99 coins that are heads up, and an unknown number of coins that are tails up. You are blindfolded and somehow can't feel the difference between the heads and tails sides of the coins. You can count the coins, put them in arbitrary many piles, flip whichever coins you want, but remember, when you flip and when you sort, you DO NOT know which ones are heads up, which are tails up. In the end, you must end up with just two piles, each containing an equal number of heads. How do you do this?

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