Problem 1 · 2009 Math Kangaroo
Easy
Fractions, Decimals & Percents
percent-multiplier
There are 200 fish in an aquarium, of which 1% are blue and the rest are yellow. How many yellow fish have to be removed to make the number of blue fish equal 2% of all the fish?
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Answer: E — 100
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Hint 1 of 2
1% of 200 is just 2 blue fish, and that count never changes—only the total does.
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Hint 2 of 2
You want 2 fish to be 2% of the new total, so the new total must be 100.
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Approach: hold the blue count fixed and shrink the total
- 1% of 200 is 2 blue fish; removing yellow fish does not change that.
- For 2 fish to be 2% of the total, the total must be 100.
- So remove 200 − 100 = 100 yellow fish.
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