1. **State the problem:** We need to find a benchmark fraction between $\frac{7}{10}$ and $\frac{2}{5}$. A benchmark fraction is a simple fraction that lies between two given fractions. 2. **Convert fractions to a common denominator:** To compare and find a fraction between them, first express both fractions with the same denominator. $$\frac{7}{10} \text{ and } \frac{2}{5} = \frac{4}{10}$$ 3. **Compare the fractions:** Now we have $\frac{7}{10}$ and $\frac{4}{10}$. Since $\frac{4}{10} < \frac{7}{10}$, the fraction between them must be greater than $\frac{4}{10}$ and less than $\frac{7}{10}$. 4. **Find a benchmark fraction:** A common benchmark fraction between these is $\frac{1}{2}$, which equals $\frac{5}{10}$. 5. **Verify:** Check that $\frac{4}{10} < \frac{5}{10} < \frac{7}{10}$, which is true. **Final answer:** The benchmark fraction between $\frac{7}{10}$ and $\frac{2}{5}$ is $\frac{1}{2}$.