

Hi its Craig again. I have a new question for you that I would really appreciate if you could help me
on. I'm a student in grade 11 (secondary).
Question: A table consists of eleven columns. Reading across the first row of the table we find the
numbers 1991, 1992, 1993,..., 2000, 2001. In the other rows, each entry in the table is 13 greater
than the entry above it, and the table continues indefinitely. If a vertical column is chosen at
random, then the probability of that column containing a perfect square is:
Possible Answers:
A) 4/11
B) 5/11
C) 1
D) 9/11
E) 7/11
Thanks, Craig.


Hi Craig,
To get a feel for it, you should add two columns at the beginning:
1989, 1990, 1991, ..., 2000, 2001
and envision also filling in the rows ABOVE this one with the same rules:
0 
1 
2 
··· 
11 
12 
13 
14 
15 
··· 
24 
26 
·
·
· 
·
·
· 
·
·
· 

·
·
· 
·
·
· 
1976 
1977 
1978 
··· 
1987 
1988 
1889 
1990 
1991 
··· 
2000 
2001 
Now which of the columns contain squares, and why?
Claude



