In order for the number in the first column to be a multiple of 5, we must write 5 in the cell corresponding to its units, that is, in row 3 and column 1. The digits in the cells corresponding to the units of the numbers that are multiple of 2, 4 and 6 must be even. Then, the number in the third row (which is a multiple of 4) begins with 5 and its remaining two digits are even. The multiples of 4 satisfying this condition, with no repeated digits and without 0, are
524, 528, 548, 564, 568, 584.
In particular, we deduce that the digit in row 3, column 3 can only be 4 or 8.
For the number in the third column, we look for the multiples of
7 beginning with an even digit, ending with
4 or
8, with no repeated digits, and without
0 and
5 among its digits. There are two:
238 and
294. Combining them with the numbers listed above, that are the candidates for the third row (note that
524 and
528 cannot be used, since
2 must be written in the first row), we obtain the following possibilities:
Board 1
Board 2
Board 3
Board 4
To determine the values of the remaining digits, we take into account that the sums of the digits in row 2 and the sum of the digits in column 2 must be multiples of 3 (in order that the corresponding numbers are multiple of 3 and 6, respectively).
Board 1: The remaining digits are 1, 6, 7, 9; thus, two are congruent with 1 modulo 3 and two are congruent with 0 modulo 3. We write the board modulo 3:
If
d=1, the number in the second row cannot be a multiple of
3 and, if
d=0, the number in the second column cannot be a multiple of
3. Then, there is no solution for Board 1.
Board 2: The remaining digits are 1, 4, 7, 9; one is congruent with 0 modulo 3 and three are congruent with 1 modulo 3. As before, by writing the board modulo 3
and considering both possible values of
d, it follows that it is not possible to fill in the board satisfying the required conditions.
Board 3: The remaining digits are 1, 3, 7, 8; two are congruent with 1 modulo 3, one is congruent with 0 modulo 3 and the remaining one is congruent with 2 modulo 3. There is a unique way to fill in the board modulo 3:
which leads to the following two solutions:
Board 4: The remaining digits are
1,
3,
6,
7; two are congruent with
0 modulo
3, and two are congruent with
1 modulo
3. There is a unique way to fill in the board modulo
3:
leading to the following solutions: