alleryStart learning →A 12g mixture is 40% vinegar by weight. How many grams of oil must be added so the new mixture is 25% vinegar?
A7.2 g
B4.8 g
C3 g
D12 g
Answer & Solution
Correct answer: A. 7.2 g
The vinegar weight stays at $(0.40)(12) = 4.8$g.
Let $x$ be grams of oil added; the new mixture weighs $12 + x$ grams.
Setting $4.8/(12 + x) = 0.25$ gives $4.8 = 0.25(12 + x) = 3 + 0.25x$.
So $1.8 = 0.25x$, and $x = 7.2$g.
**Option B is the vinegar weight, not the answer.**
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