Measurements of Length, Weight, and Time.
Roman and Arabic numerals.

Out of necessities of life, people invented both counting and measurements. At the beginning, for length measurements people used steps, hands, feet, and arms, but those measurements were inaccurate because different people produced different measurements. The metric system was introduced at the end of the 18th century in France. Scientists chose one forty-millionth of the length of the meridian as a unit of length. They called this unit of length the meter.

For a base measure of weight, they chose the gram, which is equal to the weight of 1 cubic centimeter of water at 4 degrees Celcius.

The most widely used measure of weight is the kilogram.

Table for measures of length. Base unit - the meter (m)

Partitions
NameAbbreviationContains metersNameAbbreviation1m contains
Decameterdkm10Decimeterdm10dm
Hectometerhm100Centimetercm100cm
Kilometerkm1000Millimetermm1000mm

Table for measures of weight. Base unit - the gram (g)

Abbreviation
NameAbbreviationContains gramsNameAbbreviation1gram contains
Decagramdkg10Decigramdg10dg
Hectogramhg100Centigramsg100sg
Kilogramkg1000Milligrammg1000mg

Measures of weight include also centner(c) = 100kg and ton(t) = 1000kg

Measures of time

Base measures of time are the day and the year. Other measures include the hour, the minute, and the second.

During one day (24hours) the Earth makes one full turn around its axis. During one year our planet makes approximately one turn around the Sun. According to the estimations of the astronomers, the Earth makes a turn around the Sun in 365 days 5 hours 48 minutes and 46 seconds.

In our everyday life the year most often has 365 days. Such year is a regular year. However, within 4 years the missed 5 hours 48 minutes and 46 seconds add up to approximately 1 day, therefore every fourth year has 366 days. Such year is called a leap year.

1 century = 100 years
1 year contains 12 months
1 regular year contains 365 days
1 leap year = 366 days
1 month contains 30 or 31 days, February contains 28 or 29 days (leap year).
1 day = 24 hours
1 hour = 60 minutes
1 minute = 60 seconds
1 week = 7 days

Numerals - Roman and Arabic

Characters we use to write numbers down are called numerals.
There are 10 Arabic numerals, or digits: 1, 2, 3, 4, 5, 6, 7, 8, 9, 0.
With the help of those digits we can write any number.
Numbers that we write with 1 digit are called one-digit numbers. For example 7, 3, 5, and so on.

Numbers that we write with 2 digits are called two-digit numbers. They have ones and tens. The leftmost digit indicates the number of tens. For example 25, 37.

Ones, tens, and hundreds belong to the class of simple digits.
Class of thousands.
Class of millions.
Class of billions.
For example, we read the number 75760914307 like this - 75 billions 760 millions 914 thousands and 307

In addition to Arabic numerals, sometimes we use Roman numerals.
There are seven Roman numerals:
I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000
There is no 0 among the Roman numerals.


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