Subtract Numbers and Rouding

Subtract Numbers and Addition Properties

I can subtract whole numbers with regrouping.

I can use addition properties.

Subtracting Whole Numbers

How do we subtract with regrouping?

Getting the Idea

• When you subtract, you take away from a quantity.

• There are three parts to a subtraction sentence.

• 479-236 =243

• 479 is the minuend, 236 is the subtrahend, and 243 is the difference

• You can write a subtraction problem in a column. Line up the digits on the ones place. Then subtract from right to left. Some times you may need to regroup.

Example 1

Jeff invited 62 guest to his party. 28 guest are adults. The rest are children. How many children did Jeff invite to his party?

• Strategy: Subtract to find out how many guest are children.

• Write the subtraction problem in a column. Line up the digits on the ones place.

• Since 8 is greater than 2, regroup 1 ten as 10 ones.

• Subtract the ones.

• Subtract the tens.

Example 2

• Aaron is reading a trilogy. He read 345 pages of the second book. He has 487 pages more to read to finish his book. The first book has 637 pages. How many more books does the second book have than the first book?

• Strategy: First, add to find the number of pages in the second book. Then subtract to find how many more pages are in the second book.

• Write an addition sentence to find the numebr of pages in the second book.

• Add the ones, then the tens, then the hundtreds,. Regroup if needed.

• Write a subtraction sentence to find how many more pages are in the second book. Subtract the ones, then the tens, then hundreds.

Example 3

• What is 900-300?

• Which place value will be subtracted?

• Subtract mentally.

• 900-200=600

Example 4

• Emily's family is driving 903 miles to reach their vacation site. They have already driven 289 miles. How many miles does Emily's family have left to drive?

• Strategy: Count up

• Count up from 289 to 290.

• 289+1=290

• Count up from 290 to 300.

• 290+10=300

• Subtract mentally. 903-300=603 Add the numbers you counted up to the difference. 1 + 10 +603=614

Multiple Choice

Maxwell has 373 CDs. TeLexus has 229 CDs. How many more CDs does Maxwell have than TeLexus?

• 144

• 145

• 154

• 155

Multiple Choice

Find the difference.

474-392 =

• 82

• 92

• 122

• 766

Multiple Choice

Ahmed had 250 raffle tickets to sell. There are 20 tickets left. Hoe many tickets has Ahmed sold?

• 230

• 240

• 270

• 450

Multiple Choice

A movie theater sold 692 tickets to the evening show. It sold 385 tickets to the afternoon show. How many more tickets were sold for the evening show than the afternoon show?

• 207

• 217

• 307

• 317

Multiple Choice

What is 514-100?

• 314

• 414

• 614

• 714

Multiple Choice

A town has 2 schools. There are 473 students at Smith School. Washington School has 354 students. How many more students are at Smith School than at Washington School?

• 119

• 127

• 129

• 827

Multiple Choice

Austin has 570 baseball cards. Tom has 40 less baseball cards than Henry. How many baseball cards does Tom have?

• 170

• 470

• 520

• 530

Addition Properties

Communtative, Associative, and Identity Properties

Getting the Idea

Using Addition properties can make it easier for you to add numbers. The commutative property of addition says that changing the order of the addends does not change the sum.

Example 1

• Which makes the number sentence true?

• 12+18= 18 + ____

• Strategy: Use the commutative property of addition.

• The commutative property of addition says that changing the order of the addends does not change the sum.

• 12+18=30 and 18+12=30

• The number 12 makes the sentence true.

The Associative Property

The Associative Property of Addition says that changing the grouping of the addends does not change the sum.

For example, (4+3) + 5 = 4 + (3+5)

(4+3) +5 = 7+5 4+(3+5)= 4+8

7+5=12 4+8=12

Example 2

• Find the sum.

• 3+ (17+6) = _______

• Strategy: Use the assocciative property of addition.

• Change the grouping of the addends.

• Use mental math.

• Think: 3+17 =20

• 3+(17+6) = (3+17) =6 FInd the sum of (3+17) +6.

Idenity Property of Addition

The identity property of addition says that the sum of any adend and 0 is that addend.

For example, 9+0=9 and 0+17=17.

Example 3

• What number does in the _____ to make the sentence true?

• 0+__=23

• Strategy: Use the identity property of addition.

• Look at the numbers in the number sentence 0+___=23.

• Find the other addend.

• Use the identity property of addition. When an addend is added to 0, the sum is the addend. 0+23=23

Multiple Choice

Which makes this number sentence true?

___ +7=7

• 0

• 1

• 7

• 14

Multiple Choice

Which makes the number sentence true?

(3+__) = 5= 3 +(4+5)

• 3

• 4

• 5

• 12

Multiple Choice

Which property says that the sum of any addend and 0 is that addend?

• Associative Property of Addition

• Identity Property of Addition

• Commutative Property of Addition

Multiple Choice

Which property says that changing the order of the addends does not change the sum?

• Commutative Property of Addition

• Identity Property of Addition

• Associative Property of Addition

Multiple Choice

What property says that changing the grouping of the addends does not change the sum.

• Commutative Property of Addiiton

• Associative Property of Addition

• Identtity Propery of Addition