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A puzzle based on combinatorics, which is the study of counting discrete structures. Use with [mathematics]
3
votes
Accepted
Move 10 sheep on another shore
I can, using a method devised below, do it in
Starting with a simple case, 1_0, it's pretty obvious the optimal steps are:
1_0 1_0
_10 or 10_
01_ _01
0_1 0_1
both of whi …
2
votes
Three Dice minimum value
I wrote a program to search for such dice.
It found $29$ with maximum faces of
It finds none with maximum faces of less.
Here are those dice:
The program works by first finding all ($71$ after …
6
votes
Accepted
A weird Shepherd with his sheep
The answer is
Because
I used this Python code:
Reduced bounds from before I started a search...
Because
A lower value for the upper bound is:
Lowered further by @astralfenix to
…
7
votes
Accepted
How many different kinds of rings are there?
In the language of combinatorics the number of symbols, assuming only purely rotational and reflectional geometric symmetry* is:
* as pointed out by Ian MacDonald and Silenus, this has not been guaranteed …
3
votes
Sticky sticky stick stick
This may not yet be isn't quite the best...
6
votes
Accepted
Class Seating Arrangement
The answer is
Because
As such
Note that with $9$ students this would be:
In general for squares of side $n$ these are the
...and for rectangles of sides $m,n$ the result has
5
votes
Three Stacks N cards
An upper bound is
Note that
Now we can
Some code:
def squarePairs(n):
for a in range(1, n + 1):
for b in range(a + 1, n + 1):
if ((a + b) ** .5) % 1 == 0:
…
5
votes
Arranging a long line of cards - part 2
I will put this out there, since enumeration seems to hold, although I can't quite see how it's the answer yet (i.e. what the base choices actually are that lead to this result).
What is this?
. …
14
votes
Accepted
LEVEL connections
Without allowing backtracking along edges
Since
The paths
6
votes
A weird pocket calculator
hmmn's answer is certainly correct, here is, I believe, a more formal approach.
A number, $x_0=1$, is displayed.
we may press $D-$ and produce $2x_0-1=1$, or
we may press $D+$ and produce $2x_0+1=3 …
6
votes
4
answers
544
views
My time-travelling adventure
I just had a fun visit from a time traveller and she offered to whisk me off for a whirlwind tour – she offered to take me to observe any one time for each of any choice of distinct years from $1$C.E. …
1
vote
My time-travelling adventure
Here is my generic solution.
Code to perform $_nC_k$:
def choose(n, k):
'''Returns the number of ways to choose k items from n items'''
reflect = n - k
if k > reflect:
if k > n:
…
3
votes
Accepted
The Building, the Elevator and the Milkwoman
If we also know that all the children are residents then there are
There are $80$ residents at home
All residents have the same probability, $p$, of taking the elevator at a certain time (eith …
5
votes
The L-Game of Life
The board
Because
Furthermore
4
votes