Counting fractions in a range
Consider the fraction, \( \frac{n}{d} \), where n and d are positive integers. If \( n < d \) and \( HCF(n,d) = 1 \), it is called a reduced proper fraction.
If we list the set of reduced proper fractions for \( d \leq 8 \) in ascending order of size, we get:
\[ \frac{1}{8}, \frac{1}{7}, \frac{1}{6}, \frac{1}{5}, \frac{1}{4}, \frac{2}{7}, \frac{1}{3}, \mathbf{\frac{3}{8}, \frac{2}{5}, \frac{3}{7}}, \frac{1}{2}, \frac{4}{7}, \frac{3}{5}, \frac{5}{8}, \frac{2}{3}, \frac{5}{7}, \frac{3}{4}, \frac{4}{5}, \frac{5}{6}, \frac{6}{7}, \frac{7}{8} \]
It can be seen that there are \( 3 \) fractions between \( \frac{1}{3} \) and \( \frac{1}{2} \).
How many fractions lie between \( \frac{1}{3} \) and \( \frac{1}{2} \) in the sorted set of reduced proper fractions for \( d \leq 12,000 \)?