Decimals Review Decimals Decimals are a type of

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

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. 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. 27 - 0. 09 = - 0. 7 0. 3 0. 4 - 0. 27 0. 09 0. 18

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