The Secret of TENs
When you multiply or divide by ten, or
multiples of ten (10, 100, 1,000, 10,000, 100,000, etc...), all do is move
the decimal point to the right or to the left.
Keep in mind that every
whole
number has a decimal point. All numbers to the left (<-) of the decimal
point are whole numbers. All numbers to the right (->) of a decimal point,
are fractions or parts of a whole number.
Whole numbers do not show their decimal
points. That's because the decimal point always comes after the whole
number. There is no reason to write it. The number 6 can be written as 6
or 6.0. It's easier to write 6.
14 = 14.0
7 = 7.0 65 =
65.0 134 = 134.0
MULTIPLY BY TENs
If you multiply a whole number by 10, you
would just move the imaginary decimal point one space to the
right
(=>).
10 X10 = 100
(100.0)
20 X 10 = 200
(200.0)
175 X 10 = 1750
(1,750.0)
If you multiply a whole number by any multiple
of 10, just count the zero's and move the imaginary decimal point that
many spaces to the right.
10 X100 = 1000
(10,00.0)
20 X 1000 = 20000
(20,000.0)
175 X 10,000 = 175,000
(175,000.0)
DIVIDE BY TENs
Division is just the opposite of
multiplication! That means that you move the decimal point to the LEFT
when you divide by 10 or multiples of 10.
If you divide 10 ÷10, you would move the
decimal point to the
left (<=).
You would have 1.0, or one one
10 ÷ 10 = 1 (1.0)
[NOTE: COUNT THE ZERO'S.
Then
MULTIPLY (-->) TO THE RIGHT;
DIVIDE (<--) TO THE LEFT.]
The same process applies to numbers that are
not whole. They have fractions or parts of a whole in the number.
Think of a dollar -> $1.00 (Notice that the
decimal point is after the 1.
If I have
1 dollar ($1.00) and
half of a dollar (a part),
I have $ 1.50 (notice that
the .50 represents only part of a dollar, so it goes to the right of the
decimal point).
If I multiply 1.50 by 10, I'll have 15.00! I
moved the decimal point over by 1 zero.
If I earn $ 7.65 an hour, and I've worked 10
days, how much does my company owe me?
$ 7.65 X 10 = $ 76.50
Move the decimal point over by one.
Now we can talk about the
METRIC SYSTEM of measuring. In the English
system, we measure in inches, feet, yards and miles. The metric system
uses different terms.
METER (m):
the basic unit of the metric system. It uses
the Earth as its measuring stick. One meter is said to be one
ten-millionth of the distance from the Equator to the North Pole.
CLICK the Mentor Icon to go to measuring distance with
the metric system
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