how many ml of 30% acid should be added to pure acid to make 60 ml of 55% acid

Question

 solve to find ml of acid

Answer 1

(x ml)(30%) + (60 ml - x ml)(100%) = (60 ml)(55%)

30x + 6000 - 100x = 3300

-70x = -2700

x = 38.6 mls of 30% acid

added to 21.4 ml of pure acid (assuming volumes are additive)

 

This can also be done by a process known as allegation:

 

HAVE      WANT      NEED

30%........................45..........

...............55%..................

100%......................25.........

 

Total parts = 45 + 25 = 70 parts

70 parts = 60 mls

1 part = 0.857 ml

0.857 ml x 45 parts of 30% = 38.6 mls of 30%