From the introduction, each row and each column of Word Square 8
contains the characters COIN and a blank cell in some order, so that no
character or space can be repeated in a row or a column. By clue 1, C is
the 4th letter in column 5, so C is in row 4 or row 5. If C were in row 4
of column 5, with the space then in row 5 of the column, by clue 6, the C
in column 2 would be in row 5; while by clue 9, the I in row 5 would be in
column 1. N would then be in column 3 of row 5 (clue 5), with O in column
4impossible by clue 7, since the O in column 4 is 3rd down the column.
Therefore, in clue 1, C is in column 5, row 5. By clue 6, then, the C in
column 2 must be in row 4, with the column 2 space in row 5. By clue 9,
the I in row 5 is in column 1; while by clue 5, the N in row 5 is in column
4. The O in row 5 is in column 3. The O in row 1 is the 4th letter across
the row (3) and is in either column 4 or column 5; by clue 7, the O in row 1
must be in column 5. By clue 8, the N in row 3 is in column 3 or column 4;
however, we already have N in column 4 in row 5, so the N in row 3 is in
column 3. Since the N in row 1 isn't in column 1 (2), it must be in column
2. By clue 10, the O in row 4 isn't in column 1 and is thus in column 4.
By clue 4, the I in row 2 is in column 4 or column 5. If the I in row 2
were in column 4, the space in row 2 would be in column 5. The N in column
5 would be in row 4 and the I in that column in row 3. The I in row 4
would be in column 3. However, there is now no way for I to fit in row 1.
So, in clue 4, the I in row 2 is in column 5. Row 2's N is in column 1,
with the N in row 4 in column 5. I in row 4 is in column 3, with the row
4 space in column 1. The column 2 I is in row 3, with the column 2 O in
row 2. The I in row 1 is in column 4. The O in column 1 is in row 3 and
the C in column 1 in row 1. The row 1 space is in column 3, with the column
3 C in row 2. The row 2 space is in column 4, with the column 4 C in row
3. Finally, the column 5 space is in row 3. In sum, Word Square 8
contains the word COIN as follows:
 1  2  3  4  5 
1  C  N   I  O 
2  N  O  C   I 
3  O  I  N  C  
4   C  I  O  N 
5  I   O  N  C 


