Adding to 20
Look at the picture below.
What can you see? How would you describe it to a friend?
✓ There are 9 butterflies and 11 spiders.
9 + 11 = 20
There are 20 creatures altogether.
We can use a part-whole model to show the two groups and the total of 20.
How can we show this?
We can use a part-whole model to show the two groups and the total of 20.
We can use a bar model to show this calculation.
Or a ten frame. By using a ten frame you can easily see that 20 is made up of two 10s.
You can also see that 11 is one more than 10 and 9 is one fewer, but together they total 20.
What number sentences can you make?
From this picture of two ten frames you can make four different number sentences.
11 + 9 = 20
9 + 11 = 20
20 – 11 = 9
20 – 9 = 11
This means that you can check your answer by using an inverse calculation.
11 + 9 = 20
You can check this by using the calculation:
20 – 9 = 11
Activity
Karate Cats Maths game. game
Train with the Karate Cats to become an expert in addition and subtraction, multiplication and division, place value and more!
