Let a and b be positive whole numbers such that \frac{4.5}{11}<\frac{a}{b}<\frac{5}{11}. Find the fraction \frac{a}{b} for which the sum a+b is as small as possible. Justify your answer.
Let a and b be positive whole numbers such that \frac{4.5}{11}<\frac{a}{b}<\frac{5}{11}. Find the fraction \frac{a}{b} for which the sum a+b is as small as possible. Justify your answer.