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Decimals Review

Learn about decimals, their properties, and operations. Explore significant digits, positions, and the four basic functions: addition, subtraction, multiplication, and division.

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Decimals Review

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  1. Decimals Review

  2. 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

  3. Significant Digits or Figures • They are the digits after the decimal point and after any zeros • Trailing zeros count as significant digits 0.000567 0 3 4 significant digits

  4. Significant Digits or Figures • Significant digits are the most important parts of the number • They tell you how precise a number or measurement is

  5. 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 . 0 0 0 0 tenths ten thousandths hundredths thousandths

  6. Math With Decimals Four basic functions • Add • Subtract • Multiply • Divide

  7. 0.587 0.036 + Addition • Line up the decimal points to make sure everything is in the correct column • Add like you would integers 0.587 + 0.036 = 0.623

  8. 0.4 0.27 0.6 0.05 + + Addition - Let’s Try It! 0.4 + 0.6 = 1.0 0.27 + 0. 05 = 0.32

  9. 0.587 0.036 - Subtraction • Line up the decimal points to make sure everything is in the correct column • Subtract like you would integers 0.587 - 0.036 = 0.551

  10. 0.7 0.27 0.3 0.09 - - Subtraction - Let’s Try It! 0.7 - 0.3 = 0.4 0.27 - 0. 09 = 0.18

  11. 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

  12. 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

  13. 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

  14. 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 0 8 ÷ 4 = 0.2 0.08 ÷ 0.4 = One position behind decimal

  15. Division Examples 0 6 1 ÷ 2 = 3.05 0.61 ÷ 0.2 = One position behind decimal 0 00 48 0.0048 ÷ 0.04 = ÷ 4 = 0.12 Two positions behind decimal

  16. 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

  17. 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

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