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Today we will review the Chapter: Adding & Subtracting Decimals

Good Afternoon!. Today we will review the Chapter: Adding & Subtracting Decimals. Let’s Warm up:. 1) 3 + 4 x 7 = 31. 2) (35 ÷ 5) - 7 = 0. 3) 9 + 54 ÷ 6 = 18. 4) 65 - 7 x 9 = 2. Decimals.

amayeta-johnson
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Today we will review the Chapter: Adding & Subtracting Decimals

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  1. Good Afternoon! Today we will review the Chapter: Adding & Subtracting Decimals Let’s Warm up:. 1) 3 + 4 x 7 = 31 2) (35 ÷ 5) - 7 = 0 3) 9 + 54 ÷ 6 = 18 4) 65 - 7 x 9 = 2 CONFIDENTIAL

  2. Decimals • Decimal: A number that uses place value and a decimal point to show tenths, hundredths, and thousandths. • 0.1 is a decimal number for one tenth. • 0.12 is a decimal for twelve hundredths. • 0.125 is a decimal for one hundred twenty-five thousandths. • Decimal point: A period separating the ones and the tenths in a decimal. • 2.7 • Equivalent Decimals: Decimals that name the same number. • 0.3 and 0.30 are equivalent decimals. CONFIDENTIAL

  3. Place Value • Example: • Fifty-hundredths Hundredths Ones Tenths 0 . 5 0 CONFIDENTIAL

  4. Your Turn! • Eight Hundredths Hundredths Ones Tenths 0 . 8 0 CONFIDENTIAL

  5. Place Value • Example: • Three hundred forty-four thousandths Hundredths Ones Tenths Thousandths 0 . 3 4 4 0.344 CONFIDENTIAL

  6. Your Turn • Twenty-seven thousandths Hundredths Ones Tenths Thousandths . 0 2 0 7 CONFIDENTIAL

  7. Compare & Order Decimals • Use a number line • Compare 5.7 and 5.9 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 5.7 is to the left of 5.9, 5.7 < 5.9 CONFIDENTIAL

  8. Compare & Order Decimals • Use place value • Step 1 • Line up the decimal points. Compare the ones. 5.7 5.9 • Step 2 • Compare the tenths 5.7 5.9 Think: 5 = 5 Think: 7 < 9 5.7 < 5.9 CONFIDENTIAL

  9. Your Turn • Order 5.49, 5.4, 5.57, and 6.03 from greatest to least • 6.03, 5.57, 5.49, 5.4 CONFIDENTIAL

  10. Decimals and fractions • Use models This model shows 1 This model shows 1 divided into 100 equal parts. The shaded portion shows 1/100. It can be written as 0.01 This model shows 1 divided into 10 equal parts. The shaded portion shows 1/10. It can be written as 0.1 CONFIDENTIAL

  11. Decimals and fractions • Use models • Show twenty-five hundredths as a decimal • Use graph paper to model fractions and decimals • Count 10 rows of 10 squares each for a total of 100 squares • Color 25 squares in the 100 square grid • Write the fraction of the grid that is shaded: 25/100 • Place a zero and a decimal point in front of the numerator of the fraction to make the decimal 25/100 = 0.25 CONFIDENTIAL

  12. Your Turn • Write a fraction and decimal for the shaded part. • 77/100; 0.77 CONFIDENTIAL

  13. Decimals and Mixed Numbers • Decimals greater than 1 • A mixed number is made up of a whole and a part of a whole • Example: Write as a decimal. Three and eighteen hundredths 3.18 CONFIDENTIAL

  14. Your Turn • Write a mixed number and a decimal to tell how much is shaded. 2.3 CONFIDENTIAL

  15. Rounding • Use a number line to round decimals • To round a decimal to the nearest whole number, look at the digit in the tenths place. • If the tenths digit is 5 or greater, round up to the nearest one. • If the tenths digit is less than 5, round down to the nearest one. CONFIDENTIAL

  16. Rounding • Round 5.3 to the nearest whole number • Think: 5.3 is closer to 5 than 6 • So, 5.3 rounds down to 5 • Round 5.8 to the nearest whole number • Think: 5.8 is closer to 6 than 5 • So, 5.8 rounds up to 6 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 CONFIDENTIAL

  17. Your Turn • Round 5.6 to the nearest whole number • 6 • Round 5.2 to the nearest whole number • 5 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 6.0 CONFIDENTIAL

  18. Rounding • To round to the nearest tenth, look at the digit in the hundredths place. • If the hundredths digit is 5 or greater, round up to the nearest tenth. • If the hundredths digit is less than 5, round down to the nearest tenth. CONFIDENTIAL

  19. Rounding • Round 1.56 to the nearest tenth • Think: 1.56 is closer to 1.60 than 1.50 • So, 1.56 rounds up to 1.60 • Round 1.51 to the nearest tenth • Think: 1.51 is closer to 1.50 than 1.60 • So, 1.51 rounds down to 1.50 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 CONFIDENTIAL

  20. Your Turn • Round 1.58 to the nearest tenth • 1.6 • Round 1.52 to the nearest tenth • 1.5 1.50 1.51 1.52 1.53 1.54 1.55 1.56 1.57 1.58 1.59 1.60 CONFIDENTIAL

  21. Adding Decimals • Use models to add decimals • Step 1: Draw two 10 by 10 grids on graph paper • Show 1.5 by coloring one whole grid red and coloring 50/100 of the second grid red. • Step 2: Show 0.35 by coloring 35/100 of the second grid blue. • Step 3:Count the shaded squares in each grid. Write this in decimal form. Find: 1.5 + 0.35 1.85 CONFIDENTIAL

  22. Your Turn • Find 3.38 + 0.34 = 3.72 CONFIDENTIAL

  23. Adding Decimals • Step 1: Line up the decimal points • Step 2: Add each place. Regroup if needed. Write the decimal point in the sum. • Example: Find 1.17 + 1.38 1 1.17 + 1.38 2.55 CONFIDENTIAL

  24. Your Turn • Add 0.36 + 0.46 = 0.82 CONFIDENTIAL

  25. Use Rounding Step 1: Round each addend to the nearest whole number Step 2: Add For Example: Estimate: 586.47 + 23.97 586.47 rounds to 586 23.97 rounds to 24 586 + 24 610 Estimate Sums Think: 4 < 5 Round down Think: 9 > 5 Round up CONFIDENTIAL

  26. Your Turn • Estimate the sum by rounding to the nearest whole number. 5.7 + 4.1 • 6 + 4 = 10 CONFIDENTIAL

  27. Subtracting Decimals • Use models • Example: Find 2.5 – 1.9 • Step 1:Draw three 10 by 10 grids; show 2.5 by coloring 2 whole grids and 50 small squares red. CONFIDENTIAL

  28. Subtracting Decimals • Step 2:Cross out 1 whole grid and 90 small squares to show subtracting 1.9 CONFIDENTIAL

  29. Subtracting Decimals • Step 3:Write a decimal to show the total number of shaded squares that are not crossed out. 0.6 CONFIDENTIAL

  30. Your Turn • Find the difference; 0.9 – 0.2 • 0.7 CONFIDENTIAL

  31. Step 1:Line up the decimal points. Insert a zero if needed. Step 2:Subtract each place. Regroup if needed. Write the decimal point. Step 3: You can use the inverse relationship between addition and subtraction to check. Example: 25.8 – 14.25 25.80 - 14.25 7 10 25.80 - 14.25 11.55 11.55 + 14.25 25.80 Subtracting Decimals CONFIDENTIAL

  32. Your Turn • Subtract. Check the answer. • 0.96 – 0.29 = 0.67 • Check: 0.29 + 0.67 = 0.96 CONFIDENTIAL

  33. Estimate Differences • Use Rounding • To estimate differences of decimals, round each decimal to the nearest whole number. • Then subtract the rounded numbers. • Example: Estimate 12.25 – 5.79 • 12.25: Round down to 12 • 5.79: Round up to 6 • Subtract: 12 – 6 = 6 • So 12.25 – 5.79 is about 6. CONFIDENTIAL

  34. Your Turn • Estimate. Round to the nearest whole number. • 9.7 – 4.3 = 10 – 4 = 6 CONFIDENTIAL

  35. Let us take a break! CONFIDENTIAL

  36. Jig-Saw puzzle Let us see how fast you are on this one! • Click me CONFIDENTIAL

  37. Assessment Use place value chart to read and write decimals: • 7/1,000 = seven thousandths = 0.007 • 513/1,000=five hundred thirteen thousandths = 0.513 Hundredths Ones Tenths Thousandths . 0 0 0 7 Hundredths Ones Tenths Thousandths . 5 1 0 3 CONFIDENTIAL

  38. Assessment Order from greatest to least: • 3.2, 4.5, 3.9, 4.1 • 4.5, 4.1, 3.9, 3.2 • 5.33, 4.91, 5.19, 5.52 • 5.52, 5.33, 5.19, 4.91 CONFIDENTIAL

  39. Assessment • Write a mixed number and a decimal to tell how much is shaded. 1.67 CONFIDENTIAL

  40. Assessment • Write a mixed number and a decimal to tell how much is shaded. 2.55 CONFIDENTIAL

  41. Assessment Round to the nearest tenth. • 7.24 = 7.2 Round to the nearest hundredth. • 8.236 = 8.24 CONFIDENTIAL

  42. Assessment • Add 4.718 5.200 + 3.989 13.907 • Add. Estimate to check for reasonableness. 19.76 + 9.55 = 29.31 Estimate: 20 + 10 = 30 CONFIDENTIAL

  43. Assessment • Subtract. Check answer. 1.54 - 0.39 1.15 Chcek: 1.15 + 0.39 = 1.54 • Subtract. Estimate to check for reasonableness. 7.1 – 2.70 = 7.10 – 2.70 = 4.40 Estimate: 7 – 3 = 4 CONFIDENTIAL

  44. Good Job! • You have learned a lot today!!! CONFIDENTIAL

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