42510011 0010 1010 1101 0001 0100 1011

Estimating Sums

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

How can we use what we know about rounding to estimate?

Estimating sums is best done by rounding the addends, then adding?

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

Step 1- Round the addends to the largest place value both numbers have in common.

What is the largest place value in common?

3,456 + 687

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

The hundreds place is the largest place value the two addends share in common.

3,456 + 687

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

Round both addends to the nearest hundred.

3,456 687

Use the poem to help.

Find your number.

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

Look right next door.

3,456 687

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

4 or less, just ignore.

3,456 687

Both the 5 and 8 are greater than 4, so move to the next line of the poem.

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

5 or more, add one more.

3,456 687

Both the 5 and 8 are 5 or greater, so add 1 to the numbers in the hundreds place. (4 and 6)

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

5 or more, add one more.

3,456 687

Both the 5 and 8 are 5 or greater, so add 1 to the numbers in the hundreds place. (4 and 6)

+ 1 + 1

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

3,456 687

Any number to the left remains unchanged. The 3 in 3,456 is unchanged.

+ 1 + 1

3,

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

3,456 687

Add the 1 to the place value you are rounding.

+ 1 + 1

3,5 7

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

3,456 687

All of the remaining numbers to the right become zeros.

+ 1 + 1

3,5 7 0000

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

Finally, add the rounded numbers.

3,500 + 700 4,200

4251

0011 0010 1010 1101 0001 0100 1011

Estimation and Rounding

The estimate is about 4,200.

3,456 + 687

4,200

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount.

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

241

4251

0011 0010 1010 1101 0001 0100 1011

5-2 Estimating Sums and Differences

ExampleSusan is worried that she has spent too much money. She has $256 in her checking account and has written checks for $92.69, $126.58, $9.58, and $12.39.Determine if Susan has spent too much money.

Round each check to the nearest dollar amount. 92.69

241

Since 241 < 256, Susan has enough money in her account.