There are 21*2=<<21*2=42>>42 polar bears

So the total 21+42=<<21+42=63>>63 total animals

# Answer

63
Question:
A zoo has 21 penguins and twice as many polar bears?  How many total animals do they have?
Answer:
Let's think step by step.

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63
A zoo has 21 penguins and twice as many polar bears?  How many total animals do they have?
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