Pigs in Stalls

Solution

We show all the winning solutions, because mostly they are different.

After the Contest's finish we've got quite non-standard solution to this problem from Emilie Johannes. We think it is worth to be included here along with other solutions. Therefore, we show it below as Solution 7.

Solution 1 by Jensen Lai

put 7 pigs in each of 3 stalls and put all three stalls inside a fourth stall.

Solution 2 by Nicole Takahashi

I think that there are many solns to this problem, but the common link between them all is that one stall can contain another stall. For example if I have stalls A, B, C and D set up as follows:

A: 5 pigs
B: 5 pigs
C: 5 pigs

Now there are 6 pigs remaining. That is not an odd number. But I can put stall C and the 6 remaining pigs inside of stall D. Then I have...

C: 5 pigs (as before)
D: 11 pigs (C + 6 pigs)

Solution 3 by Ben Liu

The trick is to have the stalls inside the stalls. the very inside stall has three the next stall has 2 but since it conatains the smallest stall it adds up to five. The next stall has 6 which eqaulls 11 and the next stall has 10 which eqauls 21.

Solution 4 by Chase Brechlin

You place three pigs in the first stall, four pigs in the second stall (placed around the first stall so there are actually 7 pigs in the second, five in the third stall, and 9 in the fourth stall, for a total of 21 pigs in 4 stalls.

Solution 5 by Nigel Wilson

Stall 1 : 5 pigs
Stall 2 : 7 pigs
Stall 3 : 9 pigs
Stall 4 is a large stall containing all 3 (smaller) stalls
Therefore it contains 21 pigs.

I think the puzzle is supposed to state that each stall should also contain a DIFFERENT number of pigs (?)

Solution 6 by Alex Packard

My solution is to put 7 pigs in 3 different stalls
and then put one stall around the other 3 stalls.

The fourth stall actually holds 21 pigs.

Solution 7 by Emilie Johannes

Couldn't the puzzle of fitting 21 "pigs" in 4 stalls with an odd number in each stall, be solved in the following way?