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**Adding & Subtracting Decimals**

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

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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

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**Place Value Example: Fifty-hundredths . 5 Ones Tenths Hundredths**

. 5 CONFIDENTIAL

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Your Turn! Eight Hundredths Ones Tenths Hundredths CONFIDENTIAL

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**Place Value Example: Three hundred forty-four thousandths . 3 4 4**

Ones Tenths Hundredths Thousandths . 3 4 4 0.344 CONFIDENTIAL

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**Your Turn Twenty-seven thousandths Ones Tenths Hundredths Thousandths**

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**Compare & Order Decimals**

Use a number line Compare 5.7 and 5.9 5.7 is to the left of 5.9, 5.7 < 5.9 CONFIDENTIAL

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**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 Think: 5 = 5 Think: 7 < 9 5.7 < 5.9 CONFIDENTIAL

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**Your Turn Order 5.49, 5.4, 5.57, and 6.03 from greatest to least**

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**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

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**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

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**Your Turn Write a fraction and decimal for the shaded part.**

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**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

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

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**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

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**Rounding Round 5.3 to the nearest whole number**

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 CONFIDENTIAL

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**Your Turn Round 5.6 to the nearest whole number**

Round 5.6 to the nearest whole number Round 5.2 to the nearest whole number CONFIDENTIAL

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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

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**Rounding Round 1.56 to the nearest tenth**

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 CONFIDENTIAL

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**Your Turn Round 1.58 to the nearest tenth**

Round 1.58 to the nearest tenth Round 1.52 to the nearest tenth CONFIDENTIAL

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**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: 1.85 CONFIDENTIAL

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Your Turn Find CONFIDENTIAL

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**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 1.17 + 1.38 2.55 CONFIDENTIAL

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Your Turn Add CONFIDENTIAL

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**Estimate Sums Use Rounding For Example: Estimate: 586.47 + 23.97**

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

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Your Turn Estimate the sum by rounding to the nearest whole number CONFIDENTIAL

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**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

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

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

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Your Turn Find the difference; 0.9 – 0.2 CONFIDENTIAL

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Subtracting Decimals 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 7 10 11.55 CONFIDENTIAL

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Your Turn Subtract. Check the answer. 0.96 – 0.29 CONFIDENTIAL

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**Estimate Differences Use Rounding Example: Estimate 12.25 – 5.79**

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

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**Your Turn Estimate. Round to the nearest whole number. 9.7 – 4.3**

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Let us take a break! CONFIDENTIAL

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**Let us see how fast you are on this one!**

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

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**Assessment Use place value chart to read and write decimals: 7/1,000**

513/1,000 CONFIDENTIAL

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**Assessment Order from greatest to least: 3.2, 4.5, 3.9, 4.1**

5.33, 4.91, 5.19, 5.52 CONFIDENTIAL

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

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

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**Assessment Round to the nearest tenth. 7.24**

Round to the nearest hundredth. 8.236 CONFIDENTIAL

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Assessment Add 4.718 5.2 Add. Estimate to check for reasonableness. CONFIDENTIAL

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**Assessment Subtract. Check answer. 1.54 - 0.39**

- 0.39 Subtract. Estimate to check for reasonableness. 7.1 – 2.70 CONFIDENTIAL

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Good Job! You have learned a lot today!!! CONFIDENTIAL

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