Brain Teasers, Riddles, etc...
closed account (z05DSL3A)
@chrisname
Each person paid £10 and got back £1. So they paid £9 each, totalling £27.
£25 is in the till and the bellboy has £2, totalling £27.
Each person paid £10 and got back £1. So they paid £9 each, totalling £27.
£25 is in the till and the bellboy has £2, totalling £27.
@Zykker
*grins*
It's not that simple. You're forgetting to factor in the human part of this problem.
-Albatross
*grins*
It's not that simple. You're forgetting to factor in the human part of this problem.
-Albatross
@Grey Wolf,
They paid £30 (as a group of three, so £10 each)
The bellboy was told to give them back £5 and he took £2 for himself.
So that's £28.
He then gives £1 to each of the people in the room.
That leaves £25 in the till.
It's the order you're doing it in. For example, 3 * 8 + 4 = 28 because 3 * 8 = 24 and 24 + 4 = 28, yes? But if you do the addition first, you get 8 + 4 = 12 and 3 * 12 = 36. So if you do it the wrong way round, you're bound to get the wrong answer.
I get the right answer because I calculated it in the right order. If the answer to the riddle was "it dissapears" then it wouldn't be much of a riddle...
Edit:
You're doing this:
10 - (1 * 3) = 27
27 - 2 = 25
9 * 3 = 27
27 + 2 = 29
and I'm doing this:
10 * 3 = 30
30 - (3 * 1) - 2 = 30 - 5 = 25
25 + (3 * 1) + 2 = 30
My way works and gives the correct answer both ways (when subtracting and when adding); so why is it wrong?
They paid £30 (as a group of three, so £10 each)
The bellboy was told to give them back £5 and he took £2 for himself.
So that's £28.
He then gives £1 to each of the people in the room.
That leaves £25 in the till.
It's the order you're doing it in. For example, 3 * 8 + 4 = 28 because 3 * 8 = 24 and 24 + 4 = 28, yes? But if you do the addition first, you get 8 + 4 = 12 and 3 * 12 = 36. So if you do it the wrong way round, you're bound to get the wrong answer.
I get the right answer because I calculated it in the right order. If the answer to the riddle was "it dissapears" then it wouldn't be much of a riddle...
Edit:
You're doing this:
10 - (1 * 3) = 27
27 - 2 = 25
9 * 3 = 27
27 + 2 = 29
and I'm doing this:
10 * 3 = 30
30 - (3 * 1) - 2 = 30 - 5 = 25
25 + (3 * 1) + 2 = 30
My way works and gives the correct answer both ways (when subtracting and when adding); so why is it wrong?
Last edited on
The bellboy problem is because Grey Wolf was adding the bellboy's stash in the paid amount rather than subtracting it. The bellboy didn't pay anyone so his money shouldn't be added. Instead, the patrons paid him, so his money should be subtracted:
The total bill is 25, not 30 as the riddle is suggesting.
Therefore:
Everyone pays 27 (too much)
The bellboy has 2
27 - 2 = 25 (the total bill)
EDIT: btw -- this was an awesome one
EDIT2: apparently Grey Wolf posted the solution alread and I just didn't see it. Hah
EDIT3: As for the flashlight one, I'm convinced it's not solvable unless it's a trick question and there's some maneuver they can do that we're unaware of.
As it stands the fastest way to do it would be to have Phil be the escort and bring everybody across one by one, but that totals 19 minutes.
So unless they can do something like throw the flashlight across the bridge, or carry one of them on their back, then I'm officially stumped.
The total bill is 25, not 30 as the riddle is suggesting.
Therefore:
Everyone pays 27 (too much)
The bellboy has 2
27 - 2 = 25 (the total bill)
EDIT: btw -- this was an awesome one
EDIT2: apparently Grey Wolf posted the solution alread and I just didn't see it. Hah
EDIT3: As for the flashlight one, I'm convinced it's not solvable unless it's a trick question and there's some maneuver they can do that we're unaware of.
As it stands the fastest way to do it would be to have Phil be the escort and bring everybody across one by one, but that totals 19 minutes.
So unless they can do something like throw the flashlight across the bridge, or carry one of them on their back, then I'm officially stumped.
Last edited on
For the bridge one, i think its possible, but you have to make some assumptions. Such as how far the flashlight can shine.
@Albaltross
Then Im not sure, humans have a tendency to ruin perfectly good math.
@Albaltross
Then Im not sure, humans have a tendency to ruin perfectly good math.
@Zykker: Here's what Grey Wolf intended (I think):
You have four people, who can cross the bridge in one, two, five, and ten minutes. They need a flashlight to see, and they have only one, and it can't shine very far, so if there are two people crossing, they must both cross at the speed of the slower one. There may be only two people on the bridge at any one time, and only the side that has the flashlight may send one or two people across, and when they both get to the other side, the other side gets the flashlight.
-Albatross
You have four people, who can cross the bridge in one, two, five, and ten minutes. They need a flashlight to see, and they have only one, and it can't shine very far, so if there are two people crossing, they must both cross at the speed of the slower one. There may be only two people on the bridge at any one time, and only the side that has the flashlight may send one or two people across, and when they both get to the other side, the other side gets the flashlight.
-Albatross
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Also, the flashlight puzzle is solvable. Unless I screwed up my elementary math somewhere, it is possible.
-Albatross
EDIT: 111 * 4 posts, and counting.
-Albatross
EDIT: 111 * 4 posts, and counting.
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closed account (z05DSL3A)
Re: the bridge problem.
There is no trick involved. Just move the people and add up the times taken.
Re: the hotel problem.
It is just verbal misdirection. The customers payout £27 (£9 each), £25 goes into the till and £2 goes into the pocket of the bellboy.
I'm trying to find a brain teaser that I had some time ago, it goes along the lines of the one about getting the chicken, corn, and fox across a river in a small boat. There was a larger number if things to move and different rules about what can stay with what, I think there was a mother, father, son, daughter, prisoner and guard. If anyone know what it is rules are can you post them? It took a while to solve that one.
There is no trick involved. Just move the people and add up the times taken.
Re: the hotel problem.
It is just verbal misdirection. The customers payout £27 (£9 each), £25 goes into the till and £2 goes into the pocket of the bellboy.
I'm trying to find a brain teaser that I had some time ago, it goes along the lines of the one about getting the chicken, corn, and fox across a river in a small boat. There was a larger number if things to move and different rules about what can stay with what, I think there was a mother, father, son, daughter, prisoner and guard. If anyone know what it is rules are can you post them? It took a while to solve that one.
I think the rules were:
EDIT: Extended.
There is a chicken, a cob of corn, and a fox on the same side of the river. Someone wants them all over on the other side, unspoiled. However, the chicken and the corn couldn't be alone on the same side, else the corn would be eaten. The fox and the chicken couldn't either, as then the chicken would get it. You may also only move one at a time.
That one didn't take long for me. It's very similar to the bridge problem.
-Albatross
EDIT: Extended.
There is a chicken, a cob of corn, and a fox on the same side of the river. Someone wants them all over on the other side, unspoiled. However, the chicken and the corn couldn't be alone on the same side, else the corn would be eaten. The fox and the chicken couldn't either, as then the chicken would get it. You may also only move one at a time.
That one didn't take long for me. It's very similar to the bridge problem.
-Albatross
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closed account (z05DSL3A)
The one I was talking about is http://freeweb.siol.net/danej/riverIQGame.swf
I'm sure I have seen it with english
http://www.smart-kit.com/s888/river-crossing-puzzle-hard/
I'm sure I have seen it with english
http://www.smart-kit.com/s888/river-crossing-puzzle-hard/
Last edited on
That last one Grey Wolf posted wasn't bad. It took me about 5 minutes.
I just happen to be really good at these sorts of puzzles.
-Albatross
I just happen to be really good at these sorts of puzzles.
-Albatross
No one got Albatross's.
You have a 50% chance of getting it right. (Unless they are moving things around behind the doors.)
Given three doors, and shown one that is incorrect, you now have a problem of choosing between two doors. Of the two, you still don't know which one has the car.
A 50% guess is actually pretty good chances for a gameshow.
You have a 50% chance of getting it right. (Unless they are moving things around behind the doors.)
Given three doors, and shown one that is incorrect, you now have a problem of choosing between two doors. Of the two, you still don't know which one has the car.
A 50% guess is actually pretty good chances for a gameshow.
Albatross's was super easy.
bring the chicken over
go back
bring the fox over
take the chicken back
bring the corn over
go back
bring the chicken back over.
bring the chicken over
go back
bring the fox over
take the chicken back
bring the corn over
go back
bring the chicken back over.
closed account (z05DSL3A)
| You're on Let's Make a Deal, with Monty Hall as your host. You have been told that when on the show, you will have three doors, two with donkeys and one with a car, and when you choose one, Monty will open one of the other doors, revealing a donkey, and give you a chance to switch your door. When you get on the show, indeed you do get three doors, and when you choose one, a wrong answer is shown, and you have a choice to change the door. What is the probability that changing the door will get you the car? |
Duoas,
Zykker was correct in his answer to this problem.
Put in its simplest form ('cos I can't be bothered with the maths).
The initial choice has a one in three chance of being correct and a two in three chance of being behind one of the other doors. The host removes one of the other doors, so the initial door chosen still has a one in three chance of being correct, but the other door now as a two in three chance of being correct.
I don't know what Albatross means by "It's not that simple. You're forgetting to factor in the human part of this problem." Unless it is something to do with the way the question is asked; What is the probability that changing the door will get you the car? You are twice as likely to win if you change.