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Denman 18-10-2005 11:00

coins in a dark room
 
There is a room
In the room are 50 coins
18 of them are showing tails
The rest are showing heads.

In the dark without being able to tell which way up the coins are
Sort then in to two groups
With the same amount of heads showing in each group.

answers on a post

KenWittlief 18-10-2005 12:15

Re: coins in a dark room
 
I think you grab 25 coins and flip over 7 of them

have to work this out

RogerR 18-10-2005 12:20

Re: coins in a dark room
 
Quote:

Originally Posted by KenWittlief
I think you grab 25 coins and flip over 7 of them

have to work this out

actually, i think it might be the other way around; grab 25, and flip 18.

i outta be studying for a fluid mech. exam, but this riddle keeps distracting me...

KenWittlief 18-10-2005 12:35

Re: coins in a dark room
 
{Ken starts warming up his vintage Cray 1}

MikeDubreuil 18-10-2005 12:38

Re: coins in a dark room
 
Choose a common coin type, let's say you feel US dimes. Put the dimes in one group and the rest of the coins in a different group. Bingo, 2 groups of coins :p
EDIT: Oops, forgot about the heads up part.

Jack Jones 18-10-2005 12:41

Re: coins in a dark room
 
Stand them on edge.

KenWittlief 18-10-2005 12:47

Re: coins in a dark room
 
Jack has left the box :^)

some coins wont stand on their edge

how bout, put 25 in your left pocket, and 25 in your right pocket?

(no heads are showing in either pocket)

Jack Jones 18-10-2005 12:55

Re: coins in a dark room
 
Ken took the money and ran^

The room is dark -> group anyway you want - neither group has any heads showing : zero == zero

KenWittlief 18-10-2005 13:00

Re: coins in a dark room
 
as you pick up each coin, cut it in half

put the two halfs in separate piles

or better yet, you get an elephant, a bowling ball, and 4 pounds of wax...

Denman 18-10-2005 15:15

Re: coins in a dark room
 
Quote:

Originally Posted by KenWittlief
or better yet, you get an elephant, a bowling ball, and 4 pounds of wax...

lol
i don't know the answer either
its bothering me

KenWittlief 18-10-2005 15:21

Re: coins in a dark room
 
Quote:

get an elephant, a bowling ball, and 4 pounds of wax...
the rest is intuitively obvious
this is my standard answer for all brainstorming sessions, no matter what the question or problem is

brandy836 18-10-2005 15:25

Re: coins in a dark room
 
Why don't you just turn on the light, and then flip over the coins?

Denman 18-10-2005 15:37

Re: coins in a dark room
 
Quote:

Originally Posted by brandy836
Why don't you just turn on the light, and then flip over the coins?

because it defeats the object of the excercise
lol

brandy836 18-10-2005 15:39

Re: coins in a dark room
 
I knew that, but then Ken said something about some elephant so I thought I was entitled to say something about the lights. :)

Was this a homework assignment or something?

KenWittlief 18-10-2005 15:49

Re: coins in a dark room
 
I think I reasoned it out, I had the right idea on my first post, but the wrong number

the original pile has 32 heads up, so you take 32 from the pile and flip them over. That is your second pile.

If you grabbed all 32 heads then there are no heads left in either pile

if you grabbed 18 heads and 18 tales, then you left 18 heads in the first pile, and when you flip the second pile you have 18 heads in both piles

if you grabbed 19 heads and 17 tales, then you left 17 heads in the first pile, and when you flip the second you have 17 heads and 19 tails

it works for all combinations

but I like the pocket answer better :^)


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