SOLUTION: 1. A health clinic uses a solution of bleach to sterilize petri dishes in which cultures are grown. The sterilization tank contains 100 gallons of a solution of 2% ordinary househo

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Question 9800: 1. A health clinic uses a solution of bleach to sterilize petri dishes in which cultures are grown. The sterilization tank contains 100 gallons of a solution of 2% ordinary household bleach mixed with pure distilled water. New research indicates that the concentration of bleach should be 5% for complete sterilization. How much of the solution should be drained and replaced with bleach to increase the bleach content to the recommended level?
2. A bottle contains 750 milliliters of fruit punch with a concentration of 50% pure fruit juice. Jill drinks 100 milliliters of the punch and then refills the bottle with an equal amount of a cheaper brand of punch. If the concentration of juice in the bottle is now reduced to 48%, what was the concentration in the punch that Jill added?
Answer by Earlsdon(6294) About Me  (Show Source):
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1) Original bleach solution is: 100 gallons of 2% concentration. Remove x gallons of 2% concentration and add x gallons of 100% bleach to get 100 gallons of 5% concentration. Let's set up the equation for this: Change percents to decimals.
100%280.02%29+-+x%280.02%29+%2B+x%281%29+=+100%280.05%29 Simplify and solve for x.
2+-+0.02x+%2B+x+=+5
2+%2B+0.98x+=+5
0.98x+=+3
x+=+3.06
Approximately 3.06 gallons of the original solution should be drained and replaced with bleach to attain the recommended level of concentration of 5%.
2)Original fruit punch is 750 ml of 50% concentration of pure fruit juice. Jill removes 100 ml of the 50% concentration and add 100 ml of x% concentration to get 750 ml of 48% concentration. Change the percents to decimals and set up the equation:
750%280.5%29+-+100%280.5%29+%2B+100%28x%29+=+750%280.48%29 Simplify and solve for x.
375+-+50+%2B+100x+=+360
100x+=+35
x+=+0.35
0.35 = 35%
The cheaper brand of punch had 35% concentration of pure fruit juice.