SOLUTION: A mixture contains alcohol and water in the ratio of 12:5, on adding 14 litres of wate, the ratio of alcohol to water becomes 4:3. The quality of alcohol in the mixture is?

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Question 1032038: A mixture contains alcohol and water in the ratio of 12:5, on adding 14 litres of wate, the ratio of alcohol to water becomes 4:3. The quality of alcohol in the mixture is?
Found 2 solutions by josgarithmetic, josmiceli:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
Doing as volume parts, alcohol : water,

%2812%2F17%29%2As%2F%28s%2B14%29=4%2F7 using s for quantity of the starting mixture. The proportion here presented is parts per mixture, numerator being the parts as alcohol.

The question asked for "quality" of the alcohol in the mixture. A more sensible question would be, what QUANTITY of the 12:5 MIXTURE was used to prepare the 4:3 alcohol-to-water mixture. Solving for s will give that answer.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = liters of alcohol in the
initial mixture
Let +w+ = liters of water in the
initial mixture
-----------------------------
(1) +a%2Fw+=+12%2F5+
(2) +a+%2F+%28+w+%2B+14+%29+=+4%2F3+
------------------------
(1) +5a+=+12w+
(1) +5a+-+12w++=+0+
and
(2) +3a+=+4%2A%28+w+%2B+14+%29+
(2) +3a+=+4w+%2B+56+
(2) +3a+-+4w+=+56+
(2) +9a+-+12w+=+168+
---------------------
Subtract (1) from (2)
(2) +9a+-+12w+=+168+
(1) +-5a+%2B+12w++=+0+
----------------------
+4a++=+168+
+a+=+42+
and
(1) +5a+=+12w+
(1) +w+=+%285%2F12%29%2Aa+
(1) +w+=+%285%2F12%29%2A42+
(1) +w+=+17.5+
----------------------
There are 42 liters of alcohol in the mixture
----------------------
check:
(1) +a%2Fw+=+12%2F5+
(1) +a%2Fw+=+2.4+
(1) +42%2F17.5+=+2.4+
(1) +2.4+=+2.4+
OK
(2) +a+%2F+%28+w+%2B+14+%29+=+4%2F3+
(2) +42+%2F+%28+17.5+%2B+14+%29+=+4%2F3+
(2) +42+%2F+31.5+=+4%2F3+
(2) +4%2F3+=+4%2F3+
OK