S is the set of all fractions of the form n/(n+1), Where n is a positive integer less than 20.. Than what is the product of all the fractions that are in S.
$\displaystyle \prod_{n = 1}^{19}\frac n{n + 1} = \frac 12 \cdot \frac 23 \cdot \frac 34 \cdot \frac 45 \cdot \cdots \frac {19}{20} = \frac 1{20}$ (since everything cancels, except the 1 in the numerator of the first fraction and the 20 in the denominator of the last fraction)