The amount of water (in ml) that should be added to reduce 9 ml lotion, containing 50% alcohol, to a lotion containing 30% alcohol is?

Step 1: Understand the given

Initial lotion volume = 9 ml
Alcohol concentration = 50% ⇒ Alcohol = 0.5 × 9 = 4.5 ml

Step 2: Let x ml of water be added

New total volume = 9 + x ml
Alcohol remains unchanged = 4.5 ml

Step 3: Set up the equation

New alcohol percentage = 30%

So, 4.5 / (9 + x) = 0.30

Step 4: Solve the equation

4.5 = 0.30 × (9 + x)

4.5 = 2.7 + 0.30x

4.5 - 2.7 = 0.30x

1.8 = 0.30x

x = 1.8 / 0.30 = 6

Answer: 6 ml of water should be added.