$\"\"$

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The magnitude of an earthquake is $\"\"$ .

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Where, $\"\"$ is the intensity of the quake and $\"\"$ is the intensity of a standard earthquake.

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San Francisco had a magnitude of $\"\"$ on the Richter scale, hence $\"\"$ .

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substitute $\"\"$ .

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$\"\"$

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Find the magnitude when San Francisco earthquake was $\"\"$ times as intense,.

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$\"\"$ .

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$\"\"$

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Substitute $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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Threrefore, the magnitude of the San Francisco earthquake is $\"\"$ .

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$\"\"$

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The magnitude of the San Francisco earthquake is $\"\"$ .