In the 1980's there was a song propagated by the Philippine government in mass media to help children memorize some of the more important conversions. Here's the lyrics:

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It's easy to change from english to metric

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The secret is fun if you know it

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So let's all convert from english to metric

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Let's do it, and share it, and show it

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Just multiply inches by 2.54 and you will get centimeters

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The feet multiplied by .305 will give you equivalent meters

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Just multiply pounds by .45 and you'll get kilograms it's true

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The gallons by 3.79 will turn into liters for you!

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Subtract 32 from degrees Fahrenheit, the result keep it in mind*

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For you to multiply that with five over nine,

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and you'll get Celsius just fine

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The yards and the miles are things of the past

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Use meters, and go kilometers

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So out with the english, we're modern at last

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The system of metric is (the system of metric is)

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The system of metric is better!

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"keep in mind" means until the next line, because this conversion exceptionally needs two operations and is spread over two lines.

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Shamelessly lifted from:

http://www.spiritus-temporis.com/conversion-of-units/english-to-metric-conversion-song.html