Brain Teasers

Off-Topic conversations, forum games, fun topics and pretty much anything else that doesn't fit into any other forum.
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Sat Jul 06, 2013 3:10 pm

1. There's a certain store that sells certain merchandise. It advertises: 10 for $2.00 and 100 for $3.00. How much does it cost for 500, and what does the store sell?
Answered by Insomnia: The shop sells numbers for signs and such, 500 costs $3.00.

2. There are 100 prisoners in a castle dungeon. One day, the warden gives a challenge to the prisoners.
They are told several things:
a. On the first day, each person's forehead will be painted either black or white.
b. At the end of each day, a prisoner may assert whether his forehead is painted white. If their forehead is painted white, the prisoner will go free. However, if their forehead is painted black, the prisoner will be executed.
c. If all of the prisoners with white foreheads are freed, the remaining prisoners will be freed as well.
d. If the prisoners communicate whatsoever, other than determining the color of the other foreheads, or all of the prisoners will be executed.
e. At least one forehead will be painted white.
The warden then allowed all of the prisoners to discuss a strategy for trying to free themselves, then painted all of the prisoner's foreheads white. After 100 days of doing nothing, every single prisoner asked to be freed. What was their strategy?

3. A cowboy rode into town on Tuesday, stayed three days, then rode out of town on Tuesday. How?
Answered by Insomnia: The horse is named Tuesday.

4. Twelve cents is the answer to this question.
Answered by Insomnia: Twelve cents.

5. An old man was sitting in a chair reading his book. It was quite dark out, so his wife turned off all of the lights and went to bed, but the old man continued reading. How?
Answered by Insomnia: The man is blind and reading using Braille.

6. You have 3 light bulbs in one room and their respective switches in another room separated by a thick, opaque wall. By just flipping the switches, how can you find which switch connects to which light?
Answered by Insomnia: Leave on light on, leave the second off, turn the third one on, wait a while and turn it off and check if it is warm.

7. You have an open bottle of champagne sitting on a Persian rug. How do you get the bottle off the rug without touching the bottle or knocking it over?
Answered by Akito-Agito: The rug is rolled up and the bottle slowly pushed off.

8.a. If a chicken and a half can lay an egg and a half in a day and a half, how long does it take one chicken to lay one egg?
Answered by Insomnia: A day and a half.

8.b. If three cats can catch three mice in three days, how many cats do you need to catch one hundred mice in one hundred days?
Mostly Answered by Insomnia: 4 cats.

New

9. What can one not buy with money? (As in a physical object/service, I don't want to get into all the crap about how one can/not buy love or happiness)
Answered by sburnett21: One cannot buy money with money.

10. 3 men dine at a restaurant. They decide to split the $30 bill, so they each pay the cashier $10. Just as the men leave, the cashier realizes that he had overcharged the men $5, and sends a waiter to return the $5. However, the waiter decides that it would be easier to split $3 dollars and pockets the extra $2. Since each man only paid a total of $9, $27 for all three, and the waiter secretly took $2, the total is only $29 dollars. What happened to the last $1?
Answered by Jesse_James: The math was misleading and added the wrong values. Full explanation here.

Note that some puzzles are logic and some are trickery.
Last edited by Tonex on Thu Aug 15, 2013 6:21 pm, edited 1 time in total.
Insomnia
Posts: 728
Joined: Tue Oct 13, 2009 12:00 am
Location: New Zealand
Contact:

Brain Teasers

Postby Insomnia » Sun Jul 07, 2013 7:32 am

3. horses name is tuesday - heard it before

5. he is blind

6. blow one bulb, turn second on and the third off
User avatar
Luff
Posts: 697
Joined: Sat May 22, 2010 12:00 am

Brain Teasers

Postby Luff » Sun Jul 07, 2013 10:41 am

5: fireflies.
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Sun Jul 07, 2013 1:56 pm

Insomnia is correct on 3 and 5, but 6 is not feasible in a short amount of time. Let's say they're new incandescent light bulbs and won't burn out for a couple thousand hours.
Insomnia
Posts: 728
Joined: Tue Oct 13, 2009 12:00 am
Location: New Zealand
Contact:

Brain Teasers

Postby Insomnia » Mon Jul 08, 2013 12:32 am

flick first switch on
go to sleep
wake up
flick first switch off
flick second switch on
go touch two lights that are off
burn one hand from light connected to switch one



7. if it involves a second person them to...
2. i can figure it out in my head but the word escape me, i just know each man has his own day to tell the rest who is black and none do... ill think on it a while longer
1. 500 costs $3, $1 a number for mailbox, etc

4. has me stumped
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Mon Jul 08, 2013 1:06 am

7 involves only one person
2 is petty hard to explain....
Added two more brain teasers.
Insomnia
Posts: 728
Joined: Tue Oct 13, 2009 12:00 am
Location: New Zealand
Contact:

Brain Teasers

Postby Insomnia » Mon Jul 08, 2013 7:07 am

2. each guy gets a day to alert all the rest, if 40 people had black on the 40th day someone would do something (although you say without communicating, which sort of makes me think a one-way mirror and blindfolds to let everyone look at each others forehead but this is me over-thinking things i hope) yes this isn't an answer but just me randomly typing, but quick simple answers would be:

2. Each man gets a day number to blink at the whites. if you get 99 blinks then go ask on the 100th

4. is it "$0.12"

7. it a picture of a bottle the design on the rug?

if 8's are just pure math then a day and a half and 3.03 cats
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Mon Jul 08, 2013 11:34 am

Number 2 they cannot communicate at all. No blinking at each other. It's not a picture on the rug. I don't understand how you got 3.03 cats...
Insomnia
Posts: 728
Joined: Tue Oct 13, 2009 12:00 am
Location: New Zealand
Contact:

Brain Teasers

Postby Insomnia » Mon Jul 08, 2013 4:14 pm

Since we know cats aren't a pack type hunter, we can summarize from
3 cats + 3 days = 3 mice
"1 cat takes 3 days to catch a mouse"

1 cat + 99 days = 33 mice
3 cats + 99 days = 99 mice
3 cats +100 days = 99 mice

if we bring in another cat it will be here for the whole 100 so we find how much of a cat we need for it to catch a mouse
(0.01 cats + 100 days) = (1 cat + 1 day)
(0.03 cats + 33.3 days) = (1 cat + 1 day)
now we have a cat that hunts on a 33.3 day cycle, just enough to catch an extra mouse

so in total:
3.03 cats + 100 days = 100 mice

although we will also have few extra bits of mice left over i left them out. adding bits of a cat would be bad enough,
lol
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Mon Jul 08, 2013 6:50 pm

Derp, you can't hunt part of a mouse or use part of a cat to hunt mice, so you need the fourth cat. 4 cats us the minimum number of cats you need to catch 100 mice in 100 days. (Though the cats will only need 75 days)
User avatar
Jesse James
Posts: 692
Joined: Sun Oct 11, 2009 12:00 am
Location: The Frozen Tundra of Siberia
Contact:

Brain Teasers

Postby Jesse James » Thu Jul 18, 2013 12:40 pm

Clarification Necessary:

You say that the inmates are painted only once (on the first day), and that the warden paints all of them white. From the beginning they are all painted free men and you don't specify anywhere that they are painted a new color each day.

Is this correct?
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Thu Jul 18, 2013 1:09 pm

Yes, but they cannot see their foreheads, so they do not realize that they are free men. For even more clarification, let's say that each man's top priority is not dying, so none of them will randomly guess if they are painted white or black.
User avatar
Jesse James
Posts: 692
Joined: Sun Oct 11, 2009 12:00 am
Location: The Frozen Tundra of Siberia
Contact:

Brain Teasers

Postby Jesse James » Thu Jul 18, 2013 1:39 pm

Very interesting, I've seen other brain teasers similar to this with black and white hats.

Hmm, If on the first day each of the 100 looked at one other person that also made eye contact with them then their strategy could be that on day 2 if they don't look the same person in the eye that person does not have white paint. When someone finds out that they have black paint they turn their gaze to the ground. Through this method if the paint never changes you could find out who has black paint rather quickly.

However if they all have white to begin with, then this method would resolve much quicker than the timeline put forth in your proposition and eye contact could be considered a means of communication.
User avatar
Tonex
Posts: 822
Joined: Sat Oct 29, 2011 12:00 am
Location: California Bay Area

Brain Teasers

Postby Tonex » Thu Jul 18, 2013 2:08 pm

Eye contact is communication.
User avatar
Pwnage
Posts: 438
Joined: Sun Oct 18, 2009 12:00 am
Location: San Diego, California

Brain Teasers

Postby Pwnage » Tue Jul 23, 2013 8:47 pm

Make more, Toneflex.
Pwnage.@USEast