To perform the operation \( 3\sqrt{5} \times 7\sqrt{11} \), we can multiply the coefficients (3 and 7) and the square roots together.
Here are the steps:
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Multiply the coefficients: \[ 3 \times 7 = 21 \]
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Multiply the square roots: \[ \sqrt{5} \times \sqrt{11} = \sqrt{5 \times 11} = \sqrt{55} \]
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Combine the results: \[ 3\sqrt{5} \times 7\sqrt{11} = 21\sqrt{55} \]
Since the denominator is not present in this expression and does not need to be rationalized, the final answer is: \[ \boxed{21\sqrt{55}} \]