Question 12
Hạnh writes the fractions $\frac1{98},\frac2{97},\frac3{96},\frac4{95},\ldots,\frac{95}4,\frac{96}3,\frac{97}2,\frac{98}1$. How many of the written fractions use exactly two different digits? Examples are $\frac9{90},\frac{33}{66},\frac{45}{54}$. Count digits as written, without simplifying the fractions.
