A 100-milliliter bottle of salad dressing initially consists of 80% oil and 20%
vinegar. 40% of the dressing is used, and then 4 milliliters of vinegar are
added to the bottle. What percentage of the mixture is now vinegar?
First, calculate how much oil and vinegar are in the original mixture:
Oil: 100 ml * 80% = 80 ml
Vinegar: 100 ml * 20% = 20 ml
After using 40% of the dressing, the amount of oil and vinegar left will be:
Oil: 80 ml * 60% = 48 ml
Vinegar: 20 ml * 60% = 12 ml
Now, add the 4 milliliters of vinegar to the bottle:
12 ml + 4 ml = 16 ml
Calculate the total volume of the mixture now:
80 ml (oil) + 16 ml (vinegar) = 96 ml
Calculate the percentage of the mixture that is now vinegar:
16 ml / 96 ml * 100% = 16.67%
Therefore, after adding 4 milliliters of vinegar to the bottle, the percentage of the mixture that is vinegar is 16.67%.