Extended Subtraction

​Think about this fact: 9-5=4.

Now let's extended it!

​

In your head, try 90-50 and 900-500.

​

Can you extended it more? What keeps happening??

​

If you said you are adding zeros, you are correct!

​9-4= 5

​90-40=50

​900-400=500

​9,000-4,000=5,000

​​Ok, one last challenge. Have you ever had a bigger number like 13 and had to subtract 5 from it?

Wow! That can be tough to remember that the answer is 8.

Once you get used to the answer though, you'll notice that every time you see a 3-5 in the one's place, your answer will always have an 8 in the one's place!

​

​Isn't that a neat trick?

​​Try this!

​13-8=5

​so, what is

​23-18?

​

​53-38?

​

​83-78?