Leah used $\frac{1}{2}$ cup of lemonade. Since Juan used 5 times as much lemonade, we multiply Leah's amount by 5.

$5 \times \frac{1}{2} = \frac{5}{2}$

Thus, Juan used $\frac{5}{2}$ cups of lemonade, which is also equivalent to 2 and $\frac{1}{2}$ cups as a mixed number.

Answer: $\frac{5}{2}$ or 2 $\frac{1}{2}$ cups of lemonade.

Would you like more details on this?

Here are 5 related questions:

1. What if Leah used 3/4 cup of lemonade, how much would Juan use?
2. How many cups of lemonade would they have combined?
3. What fraction represents how much lemonade Leah used compared to Juan?
4. How can you convert the mixed number 2 1/2 into an improper fraction?
5. How would the answer change if Juan used 7 times as much lemonade?

Tip: Multiplying fractions involves multiplying the numerators and denominators directly, making it a quick operation.