SOLUTION: I have on hand 98% alcohol. How much sterile water do I need to add to arrive at a solution of 20%.

Question 636323: I have on hand 98% alcohol. How much sterile water do I need to add to arrive at a solution of 20%.
Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Please re-check your problem.
Seems like we need to know the amount of 98% alcohol that you have on hand.
Hope this helps---ptaylor
The 98% alcohol is in a 5 ml vial, soooo
Let x=amount of sterile water needed
Now we know that the amount of pure alcohol before the mixture takes place(0.98)*5 has to equal the amount of pure alcohol after the mixture takes place 0.20(5+x).
Sooo our equation to solve is:
0.98*5=0.20(5+x) simplify
4.9=1+0.20x subtract 1 from each side
3.9=0.20x
x=19.5 ml---amount of sterile water needed
CK
0.98*5=0.20(5+19.5)
4.9=1+3.9
4.9=4.9
Hope this helps---ptaylor
RELATED QUESTIONS
I need to make a solution of 20% alcohol. I have on hand 98% alcohol. What is the ratio (answered by ankor@dixie-net.com)

I need to make a 20% solution of alcohol. I have on hand 70% alcohol. What formula do I (answered by ewatrrr)

A nurse has 100 ml of a solution that is 10% salt. How much sterile water must be added... (answered by josgarithmetic,ikleyn)

How many grams of powder do you need to add to 15mLs of sterile water to make a 50%... (answered by josgarithmetic)

You need a 90% alcohol solution. On hand, you have a 60 mL of a 20% alcohol mixture. You... (answered by nerdybill)

You need a 20% alcohol solution. On hand, you have a 400 mL of a 15% alcohol mixture. You (answered by josgarithmetic)

You need a 20% alcohol solution. On hand, you have a 180 mL of a 5% alcohol mixture. You... (answered by jorel555)

You need a 30% alcohol solution. On hand, you have a 385 mL of a 20% alcohol mixture. You (answered by josgarithmetic)

You need 1040 mL of a 20% alcohol solution. On hand, you have a 15% alcohol mixture. You... (answered by josgarithmetic,greenestamps,math_tutor2020)