Word problems

Question

A chemist needs 90 milliliters of a 74% acid solution but has only 68% and 9S% acid solutions available. How many milliliters of each should be mixed to get the desired solution?

Answer 1

X is the amount of the 68% acid solution

Y is the amount of the 95% acid solution

 

68% = 0.68 and 95% = 0.95

 

The amount of acid is then:

 

 0.68X + 0.95Y = 0.74*90

 

 0.68X + 0.95Y = 66.6

 

BUT X + Y = 90, so Y = 90 -X.

 

0.68X + 0.95( 90 - X) = 66.6

 

0.68X + 85.5 - 0.95X = 66.6

 

85.5 - 0.27X = 66.6

 

-0.27X = 66.6 - 85.5

 

-0.27X = -18.9

 

X = 70

 

Y = 20

 

 

 

 

 

 

 

   

Answer 2

(x ml)(68%) + [(90 - x) ml](95%) = (90 ml)(74%)

 

68x + 8550 - 95x = 6660

 

-27x = -1890

 

x = 1890/27 = 70 

90 - x = 90 - 70 = 20

 

70 ml at 68%

20 ml at 95%