Subtracting 2- and 3-Digit Numbers

Contributor: Erika Wargo. Lesson ID: 12407

What if you had $15.39 in your pocket (the one with the hole in it!) and some of it fell out. How would you figure out how much you lost? Learn to subtract large numbers while playing a fun card game!

categories

Elementary

subject
Math
learning style
Visual
personality style
Otter
Grade Level
Intermediate (3-5)
Lesson Type
Skill Sharpener

Lesson Plan - Get It!

Audio:

The new laptop costs $600. Larry has $476 saved in the bank. How much more money does Larry need before he can buy the laptop? He's counting on you to tell him!

Subtraction is the process of taking an amount away from another amount.

Subtraction is used to find the difference between numbers. As you watch the Math Antics - Multi-Digit Subtraction video about multi-digit subtraction, answer the following questions. Write the answers on a piece of paper and be ready to discuss them with a parent or teacher:

  1. Does the order of numbers matter in a subtraction problem?
  2. Which number should be written on the top of a subtraction problem?
  3. How do you know when you need to borrow in subtraction?

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When subtraction involves two- or three-digit numbers, the greatest value needs to be written first. The number with the least value is subtracted from the number with the greater value. If a number sentence is written horizontally, the number with the greater value is written first. The number with the least value is written second.

82 - 53 =

A horizontal number sentence can be rewritten vertically. The number with the greater value is written on top. The number with the least value is written below this number.

   

8

2

 

-

5

3

       

 

Line up the digits and begin subtracting in the ones place. Since 3 cannot be subtracted from 2, regroup and borrow from the tens place. Borrowing 1 ten from the tens place changes the 8 in the tens place to a 7. The ten is added to the ones place, so 2 + 10 = 12. Now, you can begin subtracting.

   

78

12

 

-

5

3

   

2

9

 

Subtract 12 - 3 = 9 in the ones place. Move to the tens place and subtract: 7 - 5 = 2, so write the 2 in the tens place. 82 - 53 = 29.

If you want to check your work, work backwards and add your solution to the number above it. The sum of the numbers should be the first number from the subtraction problem, like you see below:

   

12

9

 

-

5

3

   

8

2

 


When subtracting two- or three-digit numbers, it is important to always start subtracting in the ones place. If you need to regroup, borrow from the next place to the left, if it is not a zero. If the number is a zero, you will need to move to the left until you get a value greater than zero.

Look back at the problem from the beginning of the lesson:

The new laptop costs $600. Larry has $476 saved in the bank. How much more money does Larry need before he can buy the laptop?

First, set up your subtraction problem, with the greater value written on the top.

   

$

6

0

0

 

-

$

4

7

6

           

 

The first digit in the ones place is a zero, so move to the left to regroup. The digit in the tens place is a zero, so move to the left once more to borrow from the 6 in the hundreds place.

     

5

9

 
   

$

6

10

10

 

-

$

4

7

6

           

 

The 6 in the hundreds becomes a 5 and the 0 in the tens becomes a 10. Since we still need to subtract the ones place, we have to borrow once more. The 10 in the tens becomes a 9, and the 10 is added to the ones place. Since the digits on the top are greater than the digits on the bottom, we can subtract.

     

5

9

 
   

$

6

10

10

 

-

$

4

7

6

   

$

1

2

4

 

Check your answer with addition. Add your solution, $124, to the value above it, $476, and check to make sure you get the starting value of $600.

     

1

1

 
   

$

1

2

4

 

+

$

4

7

6

   

$

6

0

0

 

The solution of $124 was correct. Larry needs $124 more to purchase the laptop.

Discuss with a parent or teacher:

  • When setting up a subtraction problem, which number is written first? Why?
  • How do you know if you need to regroup and borrow before subtracting?

In the Got It? section, you will practice subtracting two- and three-digit numbers with interactive practice and games.

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