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2014 Math Kangaroo

Problem 17

Problem 17 · 2014 Math Kangaroo Hard
Fractions, Decimals & Percents percent-multiplier

On the packaging of a soft cheese it says: total amount of fat 24%. On the same packaging it also says: 64% fat in the dry substance. What percentage of water is in the soft cheese?

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Answer: B — 62.5%
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Hint 1 of 2
Total fat is 24% of the whole; in the dry part fat is 64%.
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Hint 2 of 2
Use those two facts to find how much of the cheese is dry, then the rest is water.
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Approach: find the dry mass, then water is the remainder
  1. Take 100 g of cheese: it contains 24 g of fat.
  2. Fat is 64% of the dry substance, so dry substance = 24 / 0.64 = 37.5 g.
  3. Water = 100 − 37.5 = 62.5 g, i.e. 62.5%.
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