Re: today's 4x4 difficult
pnm wrote:
Of the regular puzzles I enjoy doing the 4x4 difficult, trying to
find the shortest "reasoning only" path to a solution. So what
is the shortest path for today's? ....
Let's see this: Since a1 + a2 + a3 = 9 (addition rule to column 1) >>>
b2 = 2 (= 11 - 9) >>>
b4 = 3, c4 = 2.
Since d2 + b3 + c3 + d3 = 10 (= 15 - 3 - 2) and, at the same time,
a3 + b3 +c 3 + d3 = 10, we have d2 = a3 =
3, because the "3" is the only number that can be placed
simultaneously in d2 and a3.
The rest is very fast: row 2:
c2 = 1, a2 =4column 2:
c1 = 3, c3 =4, ... , the rest is obvious.