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Estimate Sums and Differences

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Round Round- to find the nearest value of a number based on a given place value.

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**Find your number. Look right next door. 4 or less, just ignore.**

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

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**Round to the nearest tens place**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest tens place 3 7 Look right next door. Find your number.

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**Round to the nearest tens place**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: If the number is 5 or greater than add 1 to the circled number. Step 5: All numbers to the right of the circled number become zeros. Rounding Round to the nearest tens place 4 3 7 3 + 1 = 4 7 is not less than 4 5 or more, add 1 more. 4 or less, just ignore.

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**37 rounded to the nearest tens place is**

Number Line 37 rounded to the nearest tens place is 40 37 40 30 37 is closer to 40 on the number line.

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**Round to the nearest tens place**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest tens place 5 2 Look right next door. Find your number.

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**Round to the nearest tens place**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: All numbers to the right of the circled number become zeros. Rounding Round to the nearest tens place Just Ignore! 5 2 2 is less than 4 4 or less, just ignore.

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**52 rounded to the nearest tens place is**

Number Line 52 rounded to the nearest tens place is 50 52 60 50 52 is closer to 50 on the number line.

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**Round to the nearest thousands place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest thousands place. 7 , 4 6 3 Look right next door. Find your number.

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**Round to the nearest thousands place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: All numbers to the right of the circled number become zeros. Rounding Round to the nearest thousands place. 7 , 4 6 3 Just Ignore! 4 = 4 4 or less, just ignore.

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**7,463 rounded to the nearest thousands place is**

Number Line 7,463 rounded to the nearest thousands place is 7,000 7,000 7,463 8,000 7,463 is closer to 7,000 on the number line.

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**Round to the nearest tenths place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest tenths place. 5 . 6 8 Look right next door. Find your number.

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**Round to the nearest tenths place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: If the number is 5 or greater than add 1 to the circled number. Step 5: All numbers to the right of the circled number become zeros. Rounding Round to the nearest tenths place. 5 . 7 6 8 8 is not less than 4 6 + 1 = 7 5 or more, add 1 more. 4 or less, just ignore.

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**5.68 rounded to the nearest tenths place is**

Number Line 5.68 rounded to the nearest tenths place is 5.7 5.68 5.7 5.6 5.68 is closer to 5.7 on the number line.

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**Round to the nearest hundredths place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest hundredths place. 6 . 4 5 8 Look right next door. Find your number.

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**Round to the nearest hundredths place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: If the number is 5 or greater than add 1 to the circled number. Step 5: All numbers to the right of the circled number become zeros. Rounding Round to the nearest hundredths place. 6 . 4 5 6 8 8 is not less than 4 5 + 1 = 6 5 or more, add 1 more. 4 or less, just ignore.

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**6.458 rounded to the nearest hundredths place is**

Number Line 6.458 rounded to the nearest hundredths place is 6.46 6.458 6.45 6.46 6.458 is closer to 6.46 on the number line.

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**Round to the nearest thousandths place.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest thousandths place. . 4 9 9 7 Look right next door. Find your number.

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**. 4 5 9 9 7 +1 4 or less, just ignore. 5 or more, add 1 more. Rounding**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: If the number is 5 or greater than add 1 to the circled number. Step 5: All numbers to the right of the circled number become zeros. Rounding Round to the nearest thousandths place. +1 . 4 5 9 9 7 10 thousandths = 1 hundredths. Time to regroup! 10 hundredths = 1 tenth. Time to regroup! 7 is not less than 4 4 + 1 = 5 9 + 1 = 10 9 + 1 = 10 5 or more, add 1 more. 4 or less, just ignore.

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**.4997 rounded to the nearest thousandths place is**

Number Line .4997 rounded to the nearest thousandths place is .5 .4997 .499 .5 .4997 is closer to .5 on the number line.

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**Round to the nearest dollar.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest dollar. $ 5 . 7 2 Look right next door. Find your number.

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**Round to the nearest dollar.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: If the number is 5 or greater than add 1 to the circled number. Step 5: All numbers to the right of the circled number become zeros. Rounding Round to the nearest dollar. $ 5 6 . 7 2 7 is not less than 4 5 + 1 = 6 5 or more, add 1 more. 4 or less, just ignore.

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**$5.72 rounded to the nearest dollar is**

Number Line $5.72 rounded to the nearest dollar is $6.00 $5.00 $5.72 $6.00 $5.72 is closer to $6.00 on the number line.

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**Round to the nearest ten cents.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Rounding Round to the nearest ten cents. $ 9 . 3 4 Look right next door. Find your number.

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**Round to the nearest ten cents.**

Step 1: Circle the digit in the place that you must round to. Step 2: Draw an arrow to the place on the right. Step 3: If the number is four or less, then the circled number stays the same. Step 4: All numbers to the right of the circled number become zeros. Rounding Round to the nearest ten cents. $ 9 . 3 4 Just Ignore! 4 = 4 4 or less, just ignore.

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**$9.34 rounded to the nearest ten cents is**

Number Line $9.34 rounded to the nearest ten cents is $9.30 $9.30 $9.34 $9.40 $9.34 is closer to $9.30 on the number line.

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**Your Turn! Round to the… …nearest ten 544 …nearest hundred 9,564**

…nearest million ,897,876 …nearest thousand 5,389 …nearest hundred thousand ,900 …nearest ten cents $8.35 …nearest thousand 5,785,965 …nearest dollar $56.39 …nearest hundred ,987 540 9,600 13,000,000 5,000 200,000 $8.40 5,786,000 $56.00 936,000

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**Your Turn! Round to the… …nearest tenth 1.24 …nearest hundredth 12.765**

12.77 0.43 0.4 8.6 2.9 156.8 3.53 0.9

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**Estimate- to find a number that is close to the exact answer.**

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**Estimation When to use estimation… When an exact answer is not needed.**

When you need to compute a problem quickly. To check your work.

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**The actual answer is 616, so our estimation is pretty accurate.**

Estimating Sums The actual answer is 616, so our estimation is pretty accurate. 5 00 + 1 00 = 6 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the hundreds place. Step 3: Now you can add 500 and 100 mentally. © 2007 M. Tallman

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**The actual answer is 5,773, so our estimation is pretty accurate**

Estimating Sums Rounding Tip: The lower the place, the more accurate the answer. However, if you round too low, your problem may be more difficult to solve. 5, Rounding Tip: The higher the place, the easier your problem will be to solve. However, your answer may not be as accurate. You could also round 5,387 to the hundreds place, 5,000 + 400 = 5,400 The actual answer is 5,773, so our estimation is pretty accurate Step 1: Rounding is always first. Decide which place to round to. Step 2: Round the first addend to the thousands place and the second addend to the hundreds place. Step 3: Now you can add 5,000 and 400 mentally. © 2007 M. Tallman

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Estimating Sums 5, You could also round 5,387 to the hundreds place, 5,000 5,400 + 400 = 5,400 5,800 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round the first addend to the thousands place and the second addend to the hundreds place. Step 3: Now you can add 5,400 and 400 mentally. © 2007 M. Tallman

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**The actual answer is 71,475, so our estimation is pretty accurate.**

Estimating Sums The actual answer is 71,475, so our estimation is pretty accurate. 44, ,578 40,000 + 30,000 = 70,000 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the ten thousands place. Step 3: Now you can add 40,000 and 30,000 mentally. © 2007 M. Tallman

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**The actual answer is $15.42, so our estimation is pretty accurate.**

Estimating Sums The actual answer is $15.42, so our estimation is pretty accurate. $ $6.75 $9.00 + $7.00 = $16.00 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the nearest dollar. Step 3: Now you can add $9.00 and $7.00, mentally. © 2007 M. Tallman

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**The actual answer is 22.2, so our estimation is pretty accurate.**

Estimating Sums The actual answer is 22.2, so our estimation is pretty accurate. 17 + 5 = 22 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the nearest whole number. Step 3: Now you can add 17 and 5 mentally. © 2007 M. Tallman

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**The actual answer is 12.5, so our estimation is pretty accurate.**

Estimating Sums The actual answer is 12.5, so our estimation is pretty accurate. 10 + 3 = 13 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the nearest whole number. Step 3: Now you can add 10 and 3 mentally. © 2007 M. Tallman

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**The actual answer is 49.1, so our estimation is pretty accurate.**

Estimating Sums The actual answer is 49.1, so our estimation is pretty accurate. 43 + 6 = 49 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the nearest whole number. Step 3: Now you can add 43 and 6 mentally. © 2007 M. Tallman

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Your Turn! Estimate Each Sum 1. $ $6.78 $20.00 + $7.00 = $27.00 500 + 700 = 1,200 100 + 500 = 600 4. 4, 5,000 + 600 = 5,600 © 2007 M. Tallman

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Your Turn! Estimate Each Sum 14 + 4 = 18 1 + 16 = 17 7. $ $102.5 $9.00 + $103.00 = $112.00 8. $ $28.70 $5.00 + $29.00 = $34.00 © 2007 M. Tallman

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Your Turn! Estimate Each Sum 9. $ $14.67 $3.00 + $15.00 = $18.00 6 + 33 = 39 11. $ $2.45 $30.00 + $2.00 = $32.00 + 13 = 13 © 2007 M. Tallman

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Estimate Differences © 2007 M. Tallman

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**496 - 112 500 - 100 = 400 Estimating Differences**

The actual answer is 384, so our estimation is pretty accurate. 500 - 100 = 400 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each number to the hundreds place. Step 3: Now you can subtract 100 from 500, mentally. © 2007 M. Tallman

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**5,251 - 896 5,000 - 900 = 4,100 Estimating Differences**

Rounding Tip: The lower the place, the more accurate the answer. However, if you round too low, your problem may be more difficult to solve. 5, Rounding Tip: The higher the place, the easier your problem will be to solve. However, your answer may not be as accurate. 5,000 - 900 = 4,100 The actual answer is 4,355, so our estimation is pretty accurate Step 1: Rounding is always first. Decide which place to round to. Step 2: Round the first addend to the thousands place and the second addend to the hundreds place. Step 3: Now you can subtract 900 from 5,000, mentally. © 2007 M. Tallman

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**52,187 - 18,978 50,000 - 20,000 = 30,000 Estimating Differences**

The actual answer is 33,209, so our estimation is pretty accurate. 52, ,978 50,000 - 20,000 = 30,000 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each addend to the ten thousands place. Step 3: Now you can subtract 20,000 from 50,000, mentally. © 2007 M. Tallman

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**$19.67 - $6.35 $20.00 - $6.00 = $14.00 Estimating Differences**

The actual answer is $13.32, so our estimation is pretty accurate. $ $6.35 $20.00 - $6.00 = $14.00 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round $19.67 to the nearest ten dollars. Round $6.35 to the nearest dollar. Step 3: Now you can subtract $6.00 from $20.00, mentally. © 2007 M. Tallman

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**17.4 - 4.8 17 - 5 = 12 Estimating Differences**

The actual answer is 12.6, so our estimation is pretty accurate. 17 - 5 = 12 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each number to the nearest whole number. Step 3: Now you can subtract 17 and 5 mentally. © 2007 M. Tallman

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**15.7 - 7.8 16 - 8 = 8 Estimating Differences**

The actual answer is 7.9, so our estimation is pretty accurate. 16 - 8 = 8 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each number to the nearest whole number. Step 3: Now you can subtract 18 and 8 mentally. © 2007 M. Tallman

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**45.8 - 6.3 46 - 6 = 40 Estimating Differences**

The actual answer is 39.5, so our estimation is pretty accurate. 46 - 6 = 40 Step 1: Rounding is always first. Decide which place to round to. Step 2: Round each number to the nearest whole number. Step 3: Now you can subtract 46 and 6 mentally. © 2007 M. Tallman

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**Estimate Each Difference**

Your Turn! Estimate Each Difference 1. $ $6.78 $20.00 - $7.00 = $13.00 500 - 200 = 300 700 - 500 = 200 4. 4, 5,000 - 900 = 4,100 © 2007 M. Tallman

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**Estimate Each Difference**

Your Turn! Estimate Each Difference 14 - 4 = 10 10 - 6 = 4 7. $ $2.59 $9.00 - $3.00 = $6.00 8. $ $8.70 $15.00 - $9.00 = $6.00 © 2007 M. Tallman

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**Estimate Each Difference**

Your Turn! Estimate Each Difference 9. $ $14.67 $23.00 - $15.00 = $8.00 66 - 33 = 33 11. $ $2.45 $30.00 - $2.00 = $28.00 12 - 1 = 11 © 2007 M. Tallman

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**Points to Keep in Mind When Estimating**

The higher the place is that you round to, the easier the estimation will be. Your answer may be less accurate though. The lower the place that you round to, the more difficult your estimation will be. Your answer will be more accurate though. Always ask yourself, “What makes the most sense?”.

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