SOLUTION: Jones has a 90% solution of boric acid in his pharmacy, which he reduces to the required strength by adding distilled water. How much solution and how much water must he use to get

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Question 675973: Jones has a 90% solution of boric acid in his pharmacy, which he reduces to the required strength by adding distilled water. How much solution and how much water must he use to get 2 quarts of 10% solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +w+ = quarts of water to be added
Let +s+ = quarts of 90% boric acid solution to be used
+.9s+ = quarts of boric acid in 90% solution
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(1) +w+%2B+s+=+2+
(2) +.9s+%2F+2+=+.1+
-----------------
(2) +.9s+=+.2+
(2) +s+=+.2%2F.9+
(2) +s+=+2%2F9+
and
(1) +w+%2B+s+=+2+
(1) +w+%2B+2%2F9+=+2+
(1) +w+=+18%2F9+-+2%2F9+
(1) +w+=+16%2F9+
16/9 of a quart of water is to be added
2/9 of a quart of 90% boric acid solution is to be used
check:
(2) +.9s+%2F+2+=+.1+
(2) +.9%2A%282%2F9%29+%2F+2+=+.1+
(2) +.2%2F2+=+.1+
(2) +.1+=+.1+