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Multiples
and sub-multiples of units
Sometimes
the measurement of physical quantities can give very large
or very small numbers. The smaller and larger units of the
basic units are multiples of ten only. They strictly follow
the decimal system. These multiples or submultiples are given
special names.
For
example, the mass of the earth and mass of the electron are
found to be as follows:
Mass
of earth (M) = 5,970,000,000,000,000,000,000,000 kg
Mass
of an electron (me) = 0.000,000,000,000,000,000,000,911
kg
You
will notice that it is not a convenient way to express the
mass of earth or the mass of an electron. It takes up space
and time to read it. Thus, for convenience, large numbers
or very small decimals are expressed in an abbreviated form.
The abbreviations in common use are based upon the powers
of ten as given in the Table.
Representation
of large and small quantities in powers of ten
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Large
quantities
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Small
quantities
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100=1
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1=100
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10=101
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0.1=10-1
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100=102
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0.01=10-2
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1,000=103
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0.001=10-3
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10,000=104
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0.0001=10-4
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100,000=105
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0.00001=10-5
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1,000,000=106
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0.000001=10-6
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Thus,
103 = 10*10*10 = 1000
and,
10-3 = 1/103 = 1/1000 = 0.001
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