tania wrote:
How much water (in grams) should be added to a 35%-solution of acid to obtain a 10%-solution?
(1) There are 50 grams of the 35%-solution.
(2) In the 35%-solution the ratio of acid to water is 7:13.
The prompt indicates that a 35% acid solution must be mixed with a 0% acid solution -- the pure water -- to yield a 10% acid solution.
Using alligation, we can determine the required ratio of 35% solution to 0% solution.
Statement 1:
Since the prompt enables us to determine the required RATIO of 35% solution to 0% solution, and Statement 1 gives us the AMOUNT of 35% solution, we can calculate the required amount of 0% solution -- in other words, the required amount of water.
SUFFICIENT.
Statement 2:
\(\frac{acid}{total} = \frac{7}{7+13} = \frac{7}{20} = \frac{35}{100} =\) 35%
Statement 2 indicates that the 35% solution is composed solely of acid and water in a 7:13 ratio, yielding a solution that is 35% acid.
Since the amoutn of 35% solution is unknown, the required amount of water cannot be determined.
INSUFFICIENT.
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