How many liters of water must be added to 15 liters of 40 % sugar syrup to obtain 30 % sugar syrup?

5L

Step-by-step explanation:

Concentration is calculated by dividing the mass of solute (sugar) with the volume of solvent (water). In this case, you want to dilute the solution from 40% to 30%. You just add more solvent/water so the solute/sugar weight will be the same. sugar weight = volume * concentration

sugar weight1 = sugar weight2

volume1 * concentration1 = volume2 * concentration2

15 L * 40% = 30% * concentration2

concentration2 = 6L / 30%

concentration2 = 20L

You need to add water and change the volume of the solution from 15L into 20L. The amount of water you need to add will be: 20L-15L = 5L