Tính bằng hai cách :

* Hướng dẫn giải

$$\begin{gathered} \left(\frac{1}{3}+\frac{1}{5}\right)\times \frac{1}{2}=\left(\frac{5}{15}+\frac{3}{15}\right)\times \frac{1}{2}=\frac{8}{15}\times \frac{1}{2}=\frac{8}{30} \\ \left(\frac{1}{3}+\frac{1}{5}\right)\times \frac{1}{2}=\frac{1}{3}\times \frac{1}{2}+\frac{1}{5}\times \frac{1}{2}=\frac{1}{6}+\frac{1}{10}=\frac{10}{60}+\frac{6}{60}=\frac{16}{60}=\frac{8}{30} \end{gathered}$$