how many mls of pure water does a pharmacist have to add to 50mls of a 15% minoxide solution to get a 10% minoxide solution?

The total solute must add up. Pure water is 0% solution:

w(0) + 50(.15) = (w+50)(.10)
7.5 = .10w + 5
.10w = 2.5
w = 25 ml

Just to check. We added 50% more volume. The volume is 3/2 what it was, so the concentration is 2/3 what it was.

To find out how many milliliters (ml) of pure water the pharmacist needs to add to 50ml of a 15% minoxidil solution in order to obtain a 10% minoxidil solution, we can use a basic equation.

Let's break down the problem step by step:

Step 1: Understand the given information.
- We have a 50ml solution of 15% minoxidil. This means that in this solution, 15% of the total volume is minoxidil, and the remaining 85% is other components (usually water or alcohol).
- We want to dilute this solution with pure water (0% minoxidil) to achieve a 10% minoxidil solution.

Step 2: Set up the equation.
We know that we have 50ml of a 15% minoxidil solution and we want to add pure water to make a 10% minoxidil solution. Let's denote the amount of pure water we need to add as 'x' ml.

The equation we can set up is:
(15% minoxidil * 50ml) + (0% minoxidil * x ml) = (10% minoxidil * (50ml + x ml))

Step 3: Solve the equation.
Let's simplify the equation:

(0.15 * 50) + (0 * x) = (0.10 * (50 + x))
7.5 + 0 = 5 + 0.10x
7.5 = 5 + 0.10x

Next, we can solve for 'x':

7.5 - 5 = 0.10x
2.5 = 0.10x
2.5/0.10 = x
25 = x

Step 4: Analyze the result.
The result 'x = 25' indicates that the pharmacist needs to add 25ml of pure water to the 50ml of the 15% minoxidil solution in order to obtain a 10% minoxidil solution.

So, to summarize: The pharmacist should add 25ml of pure water to 50ml of the 15% minoxidil solution to obtain a 10% minoxidil solution.