MATHINFINITY

Units of weights and measurements

In the TV commercial that said, "6 eggs, 2 tea spoons of sugar, little orange peels," the sugar is measured with the tea spoon! Although the metric system is the easiest system to measure and calculate, some industries in Hong Kong and Macao still use other system of units that they are used to, or even use two different systems of units at the same time.

In China, the traditional units for measuring length are "li, zhang, chi, cun, fen". "Dan, hu, sheng, ge" are units for measuring volume, and "jin, liang, qian, fen" for measuring weight. Nowadays, the common Imperials Units still in use are "mile, yard, foot, inch", "gallon, pint" and "ton, pound, ounce" for measuring length, volume and weight respectively. The International System of Units is the international standard used worldwide. Its basic units for measuring length are "meter, centimeter, millimeter", those for weight are "kilogram, gram, milligram" and those for area and volume are "square meter, cubic meter" etc. Only the units for measuring time "hour, minute, second" do not follow the decimal system.

Tools for Measurement

Ruler is the simplest tool for measuring length. However, besides straightedge and triangle ruler, there is also the garment ruler for tailoring and drawing. The steelyard balance "Cheng" that applies the law of the lever is a kind traditional Chinese measuring tool. However, it is substituted by the weighing scale, or even electronic scale, used nowadays. The measuring tools for volume are more diversified, including measuring cups used in laboratories or other kinds of containers for household or industrial use.

Length and Distance

"Foot, Inch" of the Imperial System are often used in architecture or the furniture industry. The standard dimensions of plywood are 3×6 and 4×8 feet. A double bed is 4×6 feet, whereas a single bed is 2.5×6 feet. Yard is usually used in measuring cloth and wires. The most famous application is the penalty kick of football games. In the marathon of the London 1908 Olympic Games, the total distance from the starting point at Windsor Castle to the finishing point at White City was 26 miles 385 yards, which was 42.195 km. This has become the standard length for marathons. According to the United Nations Conventions on the Law of the Sea, the Nautical Mile (=1852.4m) of the Imperial System is used to measure the distance of a country's territorial waters or exclusive economic zone.

Weight and Amount

In the wet markets, supermarkets and Chinese medicinal herbs stores in Macao, unpackaged food like rice, vegetables and meat are priced based on kilograms of the International System of Units, pounds of the Imperial System and catty of the traditional Chinese unit for weight measurement. An interesting phenomenon is that fruits tend to be priced based on their quantities nowadays. For gold, although jewelry shops use ounce or qian as units of weight when pricing their products, Troy Ounce is used as the unit of transaction for gold and precious metal when it comes to the international gold prices (1 liang = 37.429 grams = 1.20337 = 1.20337 troy ounce). For electricity, although watt is used as the unit of power, the power of air-conditioners are calculated based on horsepower (1hp= 745.69987158227022W).

Area and Volume

The land area is usually measured in square meters, but square feet or ping as used in Taiwan are commonly used in the real estate transactions (1m2 = 10.7584 ft2 =0.3025 ping). Although gallon for volume is usually labeled on the large bottled water, water companies use cubic meter as the unit for water supply. In ancient China, dou refers to a container for holding water and also a unit for measuring volume, where 1 dou is equal to 10 sheng. It can also be used to measure water, rice, oil and wine.

Did you know?

1) The ancient Egyptian thought that cubit was the most convenient unit. It is the distance from the elbow to the tip of the middle finger. It can also be divided into seven parts, each of a palm's width, or into 28 each parts, each of a finger's width. Cubit was used as the unit of standard length to measure the land area of Egypt and even accurately build the pyramids.

2) The British think that the most convenient way is to use our body for measurement. One yard is the distance from the tip of King Henry's nose to the tip of the forefinger. One foot is the length of an adult's foot. One inch is the length of one phalanx of the thumb.