1. Decimals Review by Lauren McCluskey

2. TenthHundredth Decimal Models by Christine Berg

3. Remember that each period has three place values within the period 671,690,492.36754 Tenths Hundredths Thousandths Hundreds Tens Million Ones Hundreds Tens Thousand Ones Hundreds Tens Ones Ones Ten -thousandths Hundred-thousandths by Moncia Yuskaitis

4. 0.6 or 6 tenths 0.60 or 60 hundredths Equivalent Decimals by Christine Berg

5. Use rounding When the question asks you to estimate. When you want to know if your answer is reasonable. by Monica Yuskaitis

6. Memorize this Poem Find your number. Look right next door. 4 or less just ignore. 5 or more, add 1 more. by Monica Yuskaitis

7. Round to the tenths: 75.86 75.86 75.83 75.83 75.96 75.96 75.835 75.835

8. Find your number. Look right next door. 4 or less just ignore. 5 or more, add 1 more

9. Find your number. Look right next door. 4 or less just ignore. 5 or more, add 1 more. 75. 8 6 is about 75.9 75. 8 6 is about 75.9 75. 8 3 is about 75.8 75. 8 3 is about 75.8 75. 9 6 is about 76.0 75. 9 6 is about 76.0 75. 8 35 is about 75.8 75. 8 35 is about 75.8

10. Which is greater: 0.6 or 0.58? 0.60.58 by Christine Berg

11. Which is greater: 0.400 or 0.5? 0.4000.5 by Christine Berg

12. Adding or Subtracting Decimals When adding or subtracting decimals, line them up! When adding or subtracting decimals, line them up! What is: 1. $7.54 + $3.56? 2. $15.00 - $6.27? 3. $0.75 + $1.25 + $6.79? 4. 75.425 + 3.5005? 5. 98.322 – 7.0545?

13. Adding Decimals 1. $7.54 + $3.56? 7.54 7.54 + 3.56 + 3.56 11.10 11.10 or $11.10

14. Adding or Subtracting Decimals When adding or subtracting decimals, line them up! When adding or subtracting decimals, line them up! What is: 1. $7.54 + $3.56 = $11.10 2. $15.00 - $6.27 = $8.73 3. $0.75 + $1.25 + $6.79 = $8.79 4. 75.425 + 3.5005 =78.9255 5. 98.322 – 7.0545 = 91.2675

15. Multiplying Decimals : Step 1: Multiply as if the factors were whole numbers Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

16. Step 1: 8.5 X2.5 4 2 5 1 7 0 0 2 1 2 5 next….. Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

17. Step 2: Count the total decimals places in the factors Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

18. Step 2: 8.5 X2.5 4 2 5 1 7 0 0 2 1 2 5 next….. Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

19. Step 3: Give the product the total decimal places of the factors Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

20. Step 3: 8.5 X2.5 4 2 5 1 7 0 0 2 1.2 5 Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg

21. Multiplying Decimals Why do we count the decimal places? Multiplying decimals is counter- intuitive. Multiplying decimals is counter- intuitive. What is 0.10 * 6? Think about money. 0.10 is a dime, and you have 6 of them, so how much do you have? 0.60. Think about money. 0.10 is a dime, and you have 6 of them, so how much do you have? 0.60.

22. Multiplying Decimals Or think of base ten blocks where the flat equals one hundred and each rod equals ten…

23. Multiplying Decimals 0.1 * 0.6 = Or one tenth of 6 tenths is…

24. Multiplying Decimals 0.1 * 0.6 = 0.06 Or… one tenth of 6 tenths is 6 hundredths.

25. Try it! 1. 2.50 * 0.1 ? 2. 87.655 * 0.001? 3. 125.75 * 1.0?

26. Try it! 1. 2.50 * 0.1 = 0.250 2. 87.655 * 0.001 = 0.087655 3. 125.75 * 0.10 = 12.575

27. Dividing Decimals When you divide decimals, you move the decimal in the divisor so that it’s a whole number. Then move the decimal in the dividend the same number of places.

28. How does this work? 10.00 divided by 0.10 0.10 ) 10.00 becomes: 0.10 ) 10.00 becomes: 10 ) 1000 10 ) 1000 after you move the decimal after you move the decimal two places in the divisor and two places in the divisor and two places in the dividend. two places in the dividend.

29. 10 goes into 1000 100 times so the answer is 100. Check it: 100 *.10 = 10.0 or 10.00. It works.

30. Dividing Decimals Why does this work? Why does this work? Dividing decimals can be counter- intuitive. Dividing a decimal by a decimal can give you a larger number. Now that’s odd, isn’t it? Why is this?

31. Dividing Decimals 0.1= 0.6 ÷ 6 tenths Or… there are 6 tenths in 0.6. Ask yourself: How many ___’s are in ___?

32. Try it! 1. 875.25 ÷ 0.01 ? 2. 9218.4 ÷ 0.1? 3. 722.36 ÷ 0.0001?

33. Try it! 1. 875.25 ÷ 0.01 = 87,525 2. 9218.4 ÷ 0.1 = 92,184 3. 722.36 ÷ 0.0001 = 7,223,600

34. Credits: Comparing and Rounding Decimals by Christine Berg Comparing and Rounding Decimals by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg Multiplying Decimals &Properties of Multiplication by Christine Berg Math Flash Place Value by Monica Yuskaitis Math Flash Place Value by Monica Yuskaitis Math Flash Rounding by Monica Yuskaitis Math Flash Rounding by Monica Yuskaitis