Video Transcript
We can use doubles facts to help us add. What is double eight? Use the doubles fact to find seven plus nine.
We need to use the doubles fact eight plus eight to help us find seven plus nine. What is eight plus eight or double eight? We know that eight plus two makes 10. So, we can partition our second eight into two and six because two and six makes eight. So, eight plus two is 10 plus six equals 16. So, we know that double eight is 16. We need to use the doubles fact, double eight is 16, to help us find seven plus nine.
The number seven is one less than the number eight. And nine is one more than eight. So, we could take one away from nine to make eight and then add one to seven to make it eight as well. This helps us to see that seven plus nine is equal to eight plus eight.
We took one away from the nine and added one to the seven to make eight plus eight. So, if double eight is 16, then seven plus nine equals 16. We can use doubles facts to help us add. Double eight is 16. And we can use this doubles fact to find seven plus nine, which is also 16.
