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Work Shown:
a:b = 1:3
a/b = 1/3
a*3 = b*1 ... cross multiply
3a = b
b = 3a
Since b is a one digit number, this means that the largest it can get is 9
[tex]b \le 9\\\\3a \le 9\\\\a \le \frac{9}{3}\\\\a \le 3[/tex]
The largest possible value of 'a' is 3