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 =4**column 2:

**c1 = 3, c3 =4**, ... , the rest is obvious.