Final answer:
The concentration of lemon juice in the lemonade is 33.33%, calculated by dividing the 5L of lemon juice by the total volume of 15L of all ingredients.
Step-by-step explanation:
To calculate the concentration of lemon juice in the lemonade, we sum up the total volume of all the ingredients and then divide the volume of lemon juice by this total volume. In this case, we have 5L of lemon juice, 7L of water, and 3L of sugar, giving a total volume of 5L + 7L + 3L = 15L. The concentration of lemon juice is therefore calculated as 5L / 15L, which simplifies to 1/3 or approximately 33.33%.