Understanding Subtraction

Understanding Subtraction

What is Subtraction?

• Subtraction is the opposite of Addition

• Subtraction is when you find the difference between 2 or more numbers

• Example

   $15-5=10$  

Subtraction with 1 Digit Numbers

• Subtracting with 1 digit numbers may seem easy

• Remember all your doing is finding the difference between 2 or more numbers

Subtraction with 2 Digit Numbers

• When your doing subtraction with 2 digit numbers you must remember to always start in the One's place

• Another way to remember this is that you must always do the problems from right to left

Subtraction with 2 Digit Numbers Continued

• In some or if not most Subtraction problems you will have to use Regrouping

• You have to use Regrouping when you use subtraction to find the difference between a smaller number and a bigger number

Continued

• From the example in the picture you see that you can not take 6 away from 4

• So what you have to do is borrow a ten from the 8. Which changes the 8 into a 7 and changes the 4 into a 14

• Now you can take 6 away from 14 which gives you 8. Then you take 5 away from the 7 that you now have

Poll

 $36-17=$  

• 20

• 19

• 18

Subtraction in Word Problems

• When it comes to Word Problems you have to be able to understand keywords, in order to know what kind of Word Problem it is

• Some commonly used words for subtraction problems are: Subtract, Minus, Less, Difference, Decrease, Take Away, Deduct

Example of Subtraction Word Problems

• There are 67 bird families living near the mountains. If 32 bird families flew away for winter, how many bird families were left near the mountains?

• The very first thing you must do is read the word problem in order to find out what numbers you are using and to figure out what kind of Math problem it is

• So we know from the word problem that there were 67 bird families and we know that 32 bird families left

• Reading the question " How many bird families were left near the mountains?" Since it says were left,

• The next step would be for you to use the information you found in order to turn this word problem into a Math equation

Example of Subtraction Word Problems Continued

• So by using the information we found from the word problem. The fact that there were 67 bird families and that 32 flew away. Also knowing that we have to figure out how many were left.

• The equation should look like this:

   $67-32=$  

• Then are next step would be to solve the Equation in order to find the difference or to figure out how many were left

Poll

 $67-32=$  

• 25

• 35

• 32

Example of Subtraction Word Problems Continued

• Now that we have the answer to are Equation there is still one final step left

• Since this is a word problem our answer needs to be in the form of a sentence. So our question was "There are 67 bird families living near the mountains. If 32 bird families flew away for winter, how many bird families were left near the mountains?"

• You can use the question in order to write your sentence. Since the question asks "how many bird families were left near the mountains?"

• You would write your sentence like: "There were 35 bird families left near the mountains."