Adding Three Whole Numbers 1st Grade – Associative Property of Addition
Hey kids today we are in outer space to save
some numbers. To save the numbers we will need to answer some addition problems and
use what we call the associative property. Will you help me Great lets get going.
Here is an addition problem and the answer is trapped. The only way to save the number
is to answer the question in a different way than we normally do.
Here we have 4 + 3 + 7 equals. the trapped number that we do not know yet. There are
a couple of ways we could solve this problem. We could add them in this order by counting
on, using blocks or even using a ten frame. But to free the number we have to do something
different. We are going to use our knowledge of doubles and partners of 10 to free the
answer. In this problem we could add the 4 and the
3 together and that makes 7. Now we have a 7 to add to a 7 and that is a double. If you
have learned doubles you know that 7 + 7 is 14 Wow, because I added those first two numbers
together it gave me a double which is easier to add when you know your doubles. That was
much faster than counting all the numbers one by one. This is what we call the associative
property. We are using what we know about numbers to make adding faster.
Wait a minute we just freed the 14 but now its trapped again. It looks like we still
need to look at another way of adding using the associative property. What is another
way we can add this problem faster? Here is a hint, look at the 3 and the 7. If we add
the 3 and 7 together we get 10. Many of us have memorized partners of ten. Two numbers
that add up to ten like 5 and 5 or 6 and 4 are partners of ten. So in this problem 3
and 7 is 10 and 10 plus anything is super easy. We know that 10 plus 4 is 14. We solved
the problem another way and did it way faster. We now know how to add problems like these
much faster by looking for partners of 10 and doubles. Thank you so much for helping
me free the answer, keep practicing and we will see next time, goodbye. Thank you for watching. Please share the video and Subscribe.