Unit 8: Subtraction within 20
Let's warm up our maths brains and count to 100! Join in with this video!
Today’s Learning Focus:
We have been using number lines to help us to count back when we are completing subtraction number sentences.
Today we will be subtracting numbers where they cross the tens boundary. For example, answering questions like 16 – 9. You will learn to jump back to ten first and then to jump back the remaining amount.
This concept might be a bit tricky for some of you. Using number lines and ten-frames will help you.
Here is an example:
Jill flips back from a bigger number to a smaller one.
Like yesterday's lesson, you can use a number line to count back from 16, 9 jumps to get the answer.
There are two other ways to work out this answer:
Using a tens frame to show 16 and crossing out 9 to leave you with the answer.
If you find that counting back on a number line or using a tens frame is easier for you, you can stick to these methods.
If you are more confident with your maths, you will learn how to do this method (that is pictured below), in today’s lesson. You will learn how to partition a number into two numbers to help us to start getting back to 10.
This will take some practice! Have a look at today’s video to learn more.
If you are finding this concept difficult. Just complete questions 1 and 2 on the worksheet which involves just counting back using a number line without partitioning.
I have attached a challenge sheet that accompanies today’s learning.