8.333333333333.... can be denoted using a fraction, therefore it's a rational number. It turns out that irrational numbers cannot be denoted using simple fractions.
\(8.\dot { 3 } \\ \\ =8+\frac { 1 }{ 3 } \\ \\ =\frac { 24 }{ 3 } +\frac { 1 }{ 3 } \\ \\ =\frac { 25 }{ 3 }\)