To find out how many cups of blueberries Riley needs for half a batch of muffins, you can simply take half of the original amount of blueberries required, which is \( \frac{3}{5} \).
Calculating half of \( \frac{3}{5} \):
\[ \text{Half of } \frac{3}{5} = \frac{1}{2} \times \frac{3}{5} = \frac{3 \times 1}{5 \times 2} = \frac{3}{10} \]
So, Riley will need \( \frac{3}{10} \) cups of blueberries for her half batch of muffins.