Unit 10 - Subtracting 3-Digit Numbers

-10 or -100

100

298 - 100 = ?

198

200

574 - 10 = ?

564

300

908 - 100 = ?

808

400

307 - 10 = ?

297

500

507 - 110 = ?

397

Decomposing

100

How would you decompose 356?

300 + 50 + 6

200

How many tens are in 276?

7 tens = 70

300

Did Nadia decompose 527 correctly? 

Her Work:
500 + 2 + 7

No.  

It should have been :
500 + 20 + 7

400

Did this student decompose 309 correctly?  If not, what is the correct way to decompose it.  

Their Work:  
300 + 90 + 0 

No.  300 + 90 + 0 = 390

The correct way to decompose this number is:
300 + 0 + 9

500

Who decomposed 578 correctly:  

Joan:  500 + 70 + 8

Jenn:  500 + 50 + 28

BOTH. 

Subtracting on a Number Line

100

Which side of an open number line do you start on when subtracting?

The right side. 

200

Should you jump your hundreds, tens, or ones first?

Your hundreds. 

300

Solve using a number line:  

526 - 105 = ?

421

400

Kit solved 573 - 122 on a number line.  

He hopped back 100, and landed on 473.  Then he hopped back 20 and landed on 443.  Then he went back 2 and got the answer of 441.  Kit is wrong.  Where did he go wrong?

He went back 30, instead of 20.  

500

Use a number line to solve.  

541 - 296 =?

245

Subtraction Word Problems

100

Johnny has 246 markers.  He gives 100 to Ruby.  How many markers does he have left?

246 - 100 = 146

200

Josie has 456 pencils.  She gives 10 to Charlie.  How many pencils does she have left?

446

300

Max played Fortnite for 274 hours.  Josh played for 124 hours.  How many more hours did Max play for?

273 - 124 = 150 hours more

400

Bayley ran for 767 seconds.  Daisy ran for 349 seconds.  How many more seconds did Bayley run for?

767 - 349 = 418 seconds more. 

500

Mark has 346 stickers.  He got some more stickers from his friend.  Now he has 588 stickers.  How many more did he get from his friend?

346 + ? = 588

588 - 346 = 242 stickers

Grab Bag!

100

What strategies did we use to subtract 3-digit numbers?

Place Value Chart

Decomposing

Adjusting Numbers

Number Line

200

If I need more tens, what do I need to regroup to get more?

Hundreds

Turn one hundred into ten tens. 

300

If I subtract 500 - 276, where will I need to regroup?

You will need to regroup the hundreds into tens AND the tens into ones. 

400

Why do we start on the right side of the number line when subtracting?

You need to count BACK and if you started on the left side, you couldn't go backwards. 

500

Barbie has 542 pairs of shoes.  She gives 100 to Skipper.  Then, her friend Weird Barbie gives her 120 more.  How many pairs of shoes does she have now?

562 pairs of shoes.