They used a coin called a silver dirhem as a basic measure of weight, which had a weight roughly equivalent to 45 fully grown grains of barley. Ten dirhems comprised a Wukryeh, which was translated into Latin as an "uncia" — the origin of the word "ounce. Over time, trade spread from the Mediterranean area to Europe, including the northern German City States.
As a result, a pound, 16 ounces of silver, or grains, became a commonly used measure in many regions. While England also adopted this measure, a shortage of silver caused King Offa to reduce the measurement of the pound to grains in order to use smaller coins.
Eventually, when William the Conqueror became King of England, he retained the grain pound for minting coins, but reverted to the grain pound for other purposes. Though many countries used the pound from that point onward, including England the British pound sterling, or GBP was equal to one pound-weight of silver in King Offa's time , the avoirdupois weight system was adopted during the reign of Queen Elizabeth in the 16th century.
It was a system based on the weight of coal, and its name was derived from the French phrase "avoir de pois" goods of weight or property. The avoirdupois was equivalent to 7, grains, drams of Since , the avoirdupois pound has been officially defined in most English-speaking countries as 0.
Different systems of measurement also developed over time in Asian countries. For example, in ancient India, a measure of weight called the "Satamana" was used, and was equal to the weight of gunja berries. The measurement of weight was based on the shi, which was equivalent to approximately pounds. The Chi and Zhang were units of length equivalent to approximately 25 centimeters 9.
The Chinese also developed a means to ensure accuracy through the use of a special size of bowl used for measurements that also made a specific sound when struck — if the sound was off pitch, the measurement was not accurate.
In , John Wilkins proposed a decimal system in which length, area, volume, and mass were linked to each other based on a pendulum that had a beat of one second as a base unit of length. In , Gabriel Mouton proposed a decimal system that was instead based on the circumference of the earth, an idea supported by other prominent scientists of the time such as Jean Picard and Christiaan Huygens, but that did not take hold for approximately another years.
By the mid-eighteenth century, it was clear to nations who traded and exchanged scientific ideas that standardization of weights and measures was necessary. In , Charles Maurice de Talleyrand-Perigord, the Prince of Talleyrand, approached the British represented by John Riggs-Miller and the Americans represented by Thomas Jefferson with proposals to define a common standard of length based on the length of a pendulum.
In that same year, Thomas Jefferson, presented the "Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States," which advocated for a decimal system in which units were related to each other by powers of ten.
A committee that was formed in France comprised of some of the most prominent scientists of the day came to a similar conclusion, and also proposed a decimal system for all weights and measures.
Although Congress considered Jefferson's report, it was not adopted. This allows the conversion of units by multiplying the initial measurement by one or more forms of the number 1. While the multiplication by 1 does not change the value of the measurement, it does change the measurement units.
This process uses the fact that any number or expression can be multiplied by "one" without changing its value. It may be necessary to multiply by more than one conversion ratio in more complex conversions. Use these steps to construct a unit conversion problem so one or more of the units cancel until only the desired unit remains:. Step 1. Identify the unit you have.
These are the Starting Units. Step 2. Identify the unit you want. These are the Desired Units. Step 3. Identify appropriate unit conversion factor s. These are the Linking or Ratio Unit s. Step 4. Cancel units and perform the math calculations e.
Repeat the calculation double check. Step 5. Evaluate the result. Does the answer make sense? Many unit conversion problems will require only a single unit conversion factor. However, multiple factors may be required to solve a problem. These figures illustrate both examples. Remember that Step 3, identifying the conversion factor , is often the most challenging step.
If an incorrect or approximate conversion factor is used, a correct solution will not be achieved.
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