Question

solution a is 2% alcohol and solution b is 5% alcohol. she uses 800 milliliters of solution A how many milliliters of solution b does she use if the resulting mixture is a 3% alcohol situation

Answer 1

She uses 800 mL of solution A; that is, 2% of those 800 mL is alcohol

Alcohol on a:

2% of 800 = 2*800/100 = 16mL

If we use x mL of b, the amount of alcohol is:

5% of x = 5*x/100 = x / 20

Total amount of alcohol: 16 + x/20

Total amount of solution mixture: 800 + x

The ratio:

(16 + x/20) / (800 + x) = 3%

(16 + x/20) / (800 + x) = 3/100

1600 + 5x = 2400 + 3x

Solving for x:

5x - 3x = 2400 - 1600

2x = 800

x = 400 mL

She used 400 mL of solution b