The make-24 puzzle is an oldie, but a very fun one at that.
Given four different numbers, produce—through a sequence of operations upon only those four numbers—the number twenty-four.
For example, given $2,2,3,8$ you can make $24$ by: $2\times 3\times\frac82$.
Note that each of the given numbers must be used exactly one time each in the solution, and no other digits may appear anywhere.
Here cops can submit puzzles for the robbers to solve!
As a cop, your job is to create a specific make-24 problem. You must specify:
- The four numbers a robber is allowed to use to solve your problem
- and the operations they are allowed to use (note that it's implied by default an answer should use a finite number of operations.)
For example, a good cop post may look like:
I remember being set this kind of challenge in school, one of them was quite tricky. I'll just give you the same problem our teacher gave us:
Make $24$ using $2,2,2$ and $1$ and any of the operations: multiplication, addition, subtraction, unary negation, division, factorial, square rooting, and modulus.
I managed to solve it with three of those operations, maybe you can beat me!
Somewhat-important questions raised in comments:
For the example, is the goal is to get 24 out of 2, 2, 2, 1 using 3 operations tops? An answer with 4 operations is not valid.
Actually, the cop is not allowed to limit the number of operations. However, unless the cop states otherwise, you should assume that the number of operations you use must be finite.