24 Find the value of $\frac{\frac{1}{2}-\frac{1}{3}}{\frac{1}{3}-\frac{1}{4}} \times \frac{\frac{1}{4}-\frac{1}{5}}{\frac{1}{5}-\frac{1}{6}} \times \frac{\frac{1}{6}-\frac{1}{7}}{\frac{1}{7}-\frac{1}{8}} \times \ldots \times \frac{\frac{1}{2004}-\frac{1}{2005}}{\frac{1}{2005}-\frac{1}{2006}} \times \frac{\frac{1}{2006}-\frac{1}{2007}}{\frac{1}{2007}-\frac{1}{2008}}$.
24. Answer: 1004
$\frac{1}{n}-\frac{1}{n+1}=\frac{1}{n(n+1)}$. So the numerator $=\frac{1}{2 \times 3 \times 4 \times 5 \times \ldots \times 2006 \times 2007}$ and the denominator $=\frac{1}{3 \times 4 \times 5 \times 6 \times \ldots \times 2007 \times 2008}$ which gives $\frac{2008}{2}=1004$.