Home of the Brain Teaser

[ScottH]

I love brain teasers; ALL brain teasers (math, logic, phylosophy, trick questions, you name it!). I know a few, love to make them up, and I'm betting you, fellow INTJ's have a few under your belt too.

Lets post them here. If you post one, can you prefix it with a name in brackets, this way people can answer many of them and label their answers.

Here's one I just made up:

[Gravity]
If I place an average sized grape and a ping-pong ball int he same hand, then drop them from an airplane, which will travel more distance before hitting the ground?

[qwerty]

My inital reaction is to go with the ping-pong ball because it should float around more (lighter, more surface area), but then relative to itself a grape travels further - using its own size as a distance of measurement like an ant traveling further in relation to its size than a person.

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In a souvenir toy shop, the prices are set according to the owner's whim. An airplane costs 12cents, a stamp costs 9cents, a doll costs 7cents and a top cost 5cents. According to this system, how much will the wagon cost?

[Antares]

I love brain teasers; ALL brain teasers (math, logic, phylosophy, trick questions, you name it!). I know a few, love to make them up, and I'm betting you, fellow INTJ's have a few under your belt too.

Lets post them here. If you post one, can you prefix it with a name in brackets, this way people can answer many of them and label their answers.

Here's one I just made up:

[Gravity]
If I place an average sized grape and a ping-pong ball in the same hand, then drop them from an airplane, which will travel more distance before hitting the ground?

The grape. After it hit the ground, impact would cause the grape to burst and it will bounce back up as a result... Or bits of it anyway.

But then I would never know. Assuming that your hand is big enough to control which one you toss, you could have easily dropped one and thrown one. That would have made a difference.

[Bear Warp]

I say the ping-pong ball will travel farther. A ping-pong ball is more "sensitive" to air currents than a grape is, and once it hits the ground, it'll bounce repeatedly.

[The classic farmer, goose, fox, grain, canoe, river, etc. riddle]

A farmer must transport himself, a fox, a goose, and a bag of grain across a river. The only way to cross the river is in a canoe which will fit only the farmer and one other object at a time. Only the farmer can row the canoe. The goose will eat the grain if left alone with it, and the fox will eat the goose if left alone with it. How does the farmer accomplish his task?

[RoqueBear]

Well, with wind resistance being what it is... It would depend on hight he plane was... then you would have to take into consideration the Coriolis effect with the rotation of the Earth.

[BlackHawk]

A farmer must transport himself, a fox, a goose, and a bag of grain across a river. The only way to cross the river is in a canoe which will fit only the farmer and one other object at a time. Only the farmer can row the canoe. The goose will eat the grain if left alone with it, and the fox will eat the goose if left alone with it. How does the farmer accomplish his task?

1. Goose across
2. Fox Across, Goose back
3. Grain Across
4. Goose Across

There are a bunch of different solutions

[thegnat]

Ping-pong ball.

(I'm kind of summing up a few arguments here and adding my own take)
The ping-pong ball/grape thing is just like feather vs penny. The feather floats down kind of side to side, while the penny goes straight down.

The ping-pong ball will be pushed around by air currents, the grape has enough mass to not be as affected. Now grapes aren't exactly massive, but air resistance is going to be a negligible consideration with it.

When the grape hits the ground parts of it WILL bounce back up. However, have you ever dropped an egg and been hit in the face by its splat after it hits the ground? Plus, the grape also has cells and somewhat rigid ones at that (because it's a plant). This means that the pieces it separates into aren't going to be super tiny and those won't have enough energy to go back up too far. Grapes don't even splat as easy as eggs do at least from your height (due to cellulose). Oh and the ping pong ball is VERY bouncy. It will bounce AT LEAST a few meters once it hits the ground (and of course it depends on the surface of the ground whether it will bounce a lot or a little)

Now if you drop a ping-pong ball and grape vs each other without wind, they'll both travel the same distance to the ground but the ping pong ball would bounce like mad (given the surface is conducive to bouncing). Not quite feather vs penny, but similar idea, the ping pong ball is I think a little more susceptible to wind pushing it. The ping pong ball will probably deviate more from its path.

Size-wise I don't think the grape is too much smaller than the ping pong ball. I think the air resistant floating would outweigh that by a lot.

[karen]

I realize that there are some story-telling flaws to this one, but its fun. I have had it up for my students to guess for the last week and a half, and only two out of 85 have gotten it:

A woman went to a party, poisoned the punch, had a glass of it and then left. Nobody arrived at the party after she left. The next morning, the police arrive at the scene of the party to find that everyone there died of poisoning. Everyone but the woman. They know that she poisoned the punch, but since she herself had a drink of it, they cannot prove it. How was this possible?

Hints:
#1- the poison kills instantly
#2- there is no known immunity or antidote to this poison

__________________________________________________ ________

Then there is the classic Einstien's puzzle:

There are 5 houses in five different colors. They are lined up in a row side by side. In each house lives a person with a different nationality. These 5 owners drink a certain drink, smoke a certain brand of tobacco and keep a certain pet. No owners have the same pet, smoke the same tobacco, or drink the same drink.
1. The Brit lives in the red house
2. The Swede keeps dogs as pets
3. The Dane drinks tea
4. As you look at the 5 houses from across the street, the green house is adjacent to the left of the white house
5. The person who smokes Pall Mall raises birds
6. The owner of the yellow house smokes Dunhill
7. The man living in the house right in the center drinks milk
8. The Norwegian lives in the first house
9. The man who smokes Blends lives next to the one who keeps cats
10. The man who keeps horses lives next to the one who smokes Dunhill
11. The owner who smokes Bluemaster drinks juice
12. The German smokes Prince
13. The Norwegian lives next to the blue house
14. The man who smokes Blend has a neighbor who drinks water.
15. The green house owner drinks coffee

.... who owns the fish?

(three of my students got this one after being posted for 2 weeks.)

[BlackHawk]

I realize that there are some story-telling flaws to this one, but its fun. I have had it up for my students to guess for the last week and a half, and only two out of 85 have gotten it:

A woman went to a party, poisoned the punch, had a glass of it and then left. Nobody arrived at the party after she left. The next morning, the police arrive at the scene of the party to find that everyone there died of poisoning. Everyone but the woman. They know that she poisoned the punch, but since she herself had a drink of it, they cannot prove it. How was this possible?

Hints:
#1- the poison kills instantly
#2- there is no known immunity or antidote to this poison



She froze the poison in ice cubes. Thus, she could drink the punch before the ice cubes melted without being poisoned herself.

[Bear Warp]

__________________________________________________ ________

Then there is the classic Einstien's puzzle:

There are 5 houses in five different colors. They are lined up in a row side by side. In each house lives a person with a different nationality. These 5 owners drink a certain drink, smoke a certain brand of tobacco and keep a certain pet. No owners have the same pet, smoke the same tobacco, or drink the same drink.
1. The Brit lives in the red house
2. The Swede keeps dogs as pets
3. The Dane drinks tea
4. As you look at the 5 houses from across the street, the green house is adjacent to the left of the white house
5. The person who smokes Pall Mall raises birds
6. The owner of the yellow house smokes Dunhill
7. The man living in the house right in the center drinks milk
8. The Norwegian lives in the first house
9. The man who smokes Blends lives next to the one who keeps cats
10. The man who keeps horses lives next to the one who smokes Dunhill
11. The owner who smokes Bluemaster drinks juice
12. The German smokes Prince
13. The Norwegian lives next to the blue house
14. The man who smokes Blend has a neighbor who drinks water.
15. The green house owner drinks coffee

.... who owns the fish?

(three of my students got this one after being posted for 2 weeks.)

I sent you a pm, karen, containing my solution. Don't want to potentially ruin the puzzle for others..

[karen]

She froze the poison in ice cubes. Thus, she could drink the punch before the ice cubes melted without being poisoned herself.

yes!

[ScottH]

[Gravity] SOLUTION
Ok, there is no "real" solution, because I made the question up!

But, here's what I was thinking when I wrote it.

First, bounces and such don't really matter, because the question asks distance traveled before the object "hits the ground."

But, imagine you're standing at a fair distance watching the items drop. Both will be traveling at some speed horizontally when they are dropped, and will accelerate towards the ground at 9.8m/s. They will lose their horizontal velocity, but the pingpong ball will lose it more quickly, retarded by air, because it is less dense. So, if you ignore weather and such, and imagine the arc traversed by both objects, the grape will travel farther (both laterally and in total arc distance).

But then, I never said the plane was in flight. If it's not, they'll travel about the same distance.

Unless they're outdoors, in which case any non-zero wind will cause the pingpong ball to travel farther, because it will be more influenced by wind...

So, as I said, there's no perfect answer, but some good analysis given, as hoped :-)

[muguly]

I love brain teasers; ALL brain teasers (math, logic, phylosophy, trick questions, you name it!). I know a few, love to make them up, and I'm betting you, fellow INTJ's have a few under your belt too.

Lets post them here. If you post one, can you prefix it with a name in brackets, this way people can answer many of them and label their answers.

Here's one I just made up:

[Gravity]
If I place an average sized grape and a ping-pong ball int he same hand, then drop them from an airplane, which will travel more distance before hitting the ground?

They travel the same distance. The ping pong ball just takes longer.