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# U.S. customary and metric units

Learn to sort units of measure into two categories: U.S. Customary and Metric units. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• What is 1/1000 of a litre? kilolitre or millilitre?

Also, can centi be used in all 3 units of measurement i.e. centilitre, centrigram as well as centimeter?

Lastly, same question for deci. Can it be used for decilitre and decimeter as well as decigram?
• A kilo is 1000 times greater than whatever is your starting unit, say a gram. A gram multiplied by 1000 is a kilogram, notice "kilo." A "mili" is 1/1000 of your starting unit, so it is 1000 times less than your starting unit. So in conclusion, your first answer is milli.

For your second answer, milli, or deci, are all prefixes. Milli means 1000 times less and deci means 10 times less, so you could apply those to any word, along with kilo, centi, and deka, as Sal explains at .
You can try looking here: http://en.wikipedia.org/wiki/Metric_prefix or here: http://www.purplemath.com/modules/metric.htm
• The (British) imperial system or the "US customary" system currently used in the US is so outdated. United States is one of three countries in the world that still uses these messy English units, alongside Myanmar and Liberia. It's the measurement system of the old world - these English units date back at least to the middle ages! Even the Brits have gone metric!

So what's stopping the US from adopting the International System of Units or the "metric system" as its official and primary system of measurement? Is it the cost of the transition? Or is it the American urgent need for "individuality"?

The metric system is 10 times better!
• I'll posit that Americans are, generally speaking, happy with the imperial system. They don't want to learn the new system, because this one works fine for them. Also, road signs and gas stations currently use miles. While retrofitting gas stations to use metric probably would be cheap (though there isn't much demand for them to do so), changing old road signs from using miles to kilometers would be very expensive and would require a complete revamp of our road systems.
• Why is metric better?
• Metric has more value and responsibilities. It is common around the world. It is the main system to measure. It used in India,Germany.Russia,Netherlands and many more sights in the world. Our Us Customary System has less responsibilities cause of the metric system
• How did the U.S. get this separate system of measurement in the first place?
And why did the U.S. government decide not use the metric system or SI units?
• The metric system came along after the system the US still uses. Years ago, most other countries went metric. The US tried to, but Americans just wouldn't go along.
• At -, Sal mentions that there are two measurements called "ounces." how did something like this happen? I know that in the metric system, the units of mass, volume, and distance are connected, for one cubic centimeter = one milliliter, and the gram was originally calculated as the mass of one milliliter of water. However, I want to know if there is any connection between fluid ounces (for volume) and ounces (for weight).
• Historically, a fluid ounce was equal to the volume of one ounce of a liquid (water, beer, wine, etc.) - but this meant that the actual volume of 1 fluid ounce would differ from one substance to another.

At present, 1 oz of pure water is roughly equal to 1 fl oz of pure water. If you measure 1 fl oz of other liquids, however, they may or may not weigh 1 oz.

Hope this helps!
• why is it that the United States does not use the metric system?
• In the United States, students have been learning both systems for at least 40 years. And both systems are pretty widely understood and used in the U.S.

Becasue the US Government has limited power to demand that everyone use only the decimal system, both systems have continued to be used because that it what people choose to do.
• Why is the US customary system based on ambiguous numbers like 3, 12, and 1280?
• There not ambiguous, but the customary measurements are all sorts of orquard and outdated.

However a small benifit is that a high proportion of natural numbers smaller than numbers like 12 and 360 are factors of those numbers, unlike 10 and 1000.

10: 2, 5
12: 2, 3, 4, 6
1000: 16 factors, lowest few being: 2, 4, 5, 8, 10
360: 24 factors, including 2, 3, 4, 5, 6, 7, 8, 9, 10