\( \begin{array}{lllll}\text { (5.1) } \frac{1}{2} \times \frac{3}{5} & 5.2 & \frac{5}{7} \times \frac{8}{9} & \text { 5.3 } & \frac{1}{2} \times \frac{4}{5}\end{array} \)

When multiplying fractions, simply multiply the numerators together and the denominators together. For example, in \( \frac{1}{2} \times \frac{3}{5} \), you multiply 1 (numerator) by 3 (numerator) to get 3, and 2 (denominator) by 5 (denominator) to get 10, resulting in \( \frac{3}{10} \). Often, a common mistake is forgetting to simplify the result. Take \( \frac{5}{7} \times \frac{8}{9} \); after calculating \( \frac{40}{63} \), it’s already in simplest form since 40 and 63 share no common factors. Always double-check for the possibility of simplifying your final answer!