Transcript Decimals-long

Decimals Review
Decimals
• Decimals are a type of fractional number
• The denominator is always a power of 10
• A decimal point is used to show that it is less than 1
The decimal .5 represents the fraction 5/10
The decimal .25 represents the fraction 25/100
What decimal is represented by the fraction 461/1000?
0.461
Significant Digits or Figures
• They are the digits after the decimal point and
after any zeros
• Trailing zeros count as significant digits
0.0005670
4 significant digits
3
Significant Digits or Figures
• Significant digits are the most important
parts of the number
• They tell you how precise a number
or measurement is
Positions
• Positions tell us how much each digit is worth,
like they do for whole numbers
• They are the number of spaces each digit is
behind the decimal point
0.0000
tenths
hundredths
ten thousandths
thousandths
Math With Decimals
Four basic functions
•
Add
•
Subtract
•
Multiply
•
Divide
Addition
• Line up the decimal points to make sure
everything is in the correct column
• Add like you would integers
0.587 + 0.036 =
0.587
+ 0.036
0.623
Addition - Let’s Try It!
0.4
0.4 + 0.6 =
+ 0.6
1.0
0.27 + 0. 05 =
0.27
+ 0.05
0.32
Subtraction
• Line up the decimal points to make sure
everything is in the correct column
• Subtract like you would integers
0.587 - 0.036 =
-
0.587
0.036
0.551
Subtraction - Let’s Try It!
0.7 - 0.3 =
-
0.7
0.3
0.4
-
0.27
0.09
0.18
0.27 - 0. 09 =
Multiplication
• Move the decimal point of the first number to the left
one space for each position behind the decimal point
of the second number
• Multiply that new number by the whole number value
of the second number (ignore decimal point)
• Make sure to fill in any missing zeros
0.07 x 0.3 = 0 0 07 x 3 = 0.021
One position
behind decimal
Multiplication Examples
0.61 x 0.2 = 0 0 61 x 2 = 0.122
One position
behind decimal
0.0048 x 0.04 = 0 00 0048 x 4 = 0.000192
Two positions
behind decimal
Multiplication - Let’s Try It!
0.01 x 0.1 = 0.001
0.33 x 0.2 = 0.066
0.09 x 0.02 = 0.0018
0.012 x 0.7 = 0.0084
0.4 x 0.007 = 0.0028
0.5 x 0.001 = 0.0005
Division
• Like multiplication, but move the decimal point of the
first number to the right one place for each position
behind the decimal point of the second number
• Divide the new number by the whole number value
of the second number (ignore decimal point)
0.08 ÷ 0.4 = 0 0 8 ÷ 4 = 0.2
One position
behind decimal
Division Examples
0.61 ÷ 0.2 = 0 6 1 ÷ 2 = 3.05
One position
behind decimal
0.0048 ÷ 0.04 = 0 00 48 ÷ 4 = 0.12
Two positions
behind decimal
Division - Let’s Try It!
0.01 ÷ 0.1 = 0.1
0.33 ÷ 0.2 = 1.65
0.09 ÷ 0.02 = 4.5
0.009 ÷ 0.03 = 0.3
0.4 ÷ 0.008 = 50
0.56 ÷ 0.07 = 8
Review
• Decimals are fractional numbers where the
denominators are powers of 10
• Significant digits tell you how precise the number is
• Decimals add and subtract like integers
• Multiplying two decimals makes a smaller decimal
• Dividing two decimals makes a larger number