Question

you need 420 mL of a 65% alcohol solution. on hand you have a 15% alcohol mixture and a 85% alcohol mixture. how much of each mixture will you need to obtain the desired solution.you will need how much mL of the 15% soulutionandhow much mL of the 85% solution

Answer 1

let we have the amount of 15 % alcohol mixture is 'a'

let we have the amount of 85 % alcohol mixture is 'b'

so total is

a+ b = 420 ml ..... (1)

total amount of alcohol in the mixture is

a x 0.15 + b x 0.85 = 420 x 0.60

15a + 85b = 420 x 60

multiply equation 1 by 15

15a + 15 b = 420 x 15 .....(3)

15 a + 85 b = 420 x 60 ...... (2)

subtract equation (3) from (2)

85b - 15 b = 420 (60 - 15 )

70b = 420 x 45

b = 6 x 45

b = 270 ml

a+ b = 420

a + 270 = 420

a = 420 - 270

a = 150

so the 15% solution is 150 ml

and the 85% solution​ is 270 ml