Consider a $5\times5$ grid of math operators and numbers that encodes 8 math equations:
A + B = C
= + + + +
D + E = F
+ = = = =
G = H + I
There are 3 horizontal equations, 3 vertical, and 2 diagonal. Specifically:
A + B = C
D + E = F
H + I = G
D + G = A
B + E = H
C + F = I
A + E = I
C + E = G
However, to make the grid less strict, each equation has 3 additional allowed forms:
The
+
can be replaced with*
. e.g.A * B = C
. (We'll avoid- / ^
since they aren't commutative.)The
+
and=
can be swapped. e.g.A = B + C
.Both of the above. e.g.
A = B * C
.
Thus you can massage the equations a bit in order to form a more workable grid. For example, it might look like:
A * B = C
+ = * * +
D = E * F
= = = + =
G * H = I
The question is: Can the letters A
through I
be replaced with all one-digit numbers 1
through 9
in any order such that all 8 grid equations are satisfied?
Are there lots of solutions or none at all?
(Bonus: What if -
or /
or ^
is allowed to be an operator (and you make some assumptions about reading direction).)
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