Here’s the identification of each number along with the most specific set it belongs to:
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0.121212... - Rational Number (it can be expressed as a fraction, specifically 12/99 or 4/33).
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√144 - Whole Number (since √144 = 12, which is a whole number).
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√47 - Irrational Number (since 47 is not a perfect square, √47 cannot be simplified to a fraction).
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-9 - Integer (it is a whole number but specifically a negative whole number).
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0 - Natural Number (note that traditionally, natural numbers start from 1, but in some definitions, 0 is included).
So the final assignments are:
- 0.121212... - Rational Number
- √144 - Whole Number
- √47 - Irrational Number
- -9 - Integer
- 0 - Natural Number
(Note: The classification of 0 as a natural number can vary depending on the definition used, so it might be valid to say that 0 belongs to the set of Integers instead. Here, I have categorized it based on the definition including 0 as a natural number.)