Video Transcript
Calculate four times nine.
When we multiply by nine, we can use our multiplication facts and patterns to help us. And the first multiplication fact is one times nine is nine. Then we need to find two times nine, three times nine, and four times nine. In the nine times table, this is the pattern. The tens digit increases by one each time.
In other words, we add one to the tens digit each time. And the ones digit decreases by one each time. Or in other words, we take away one each time. This column represents the tens digit. And this column represents the ones digit. There’s nothing in this column. There are no tens in nine.
But we still have to increase this digit by one. So we have to add one. To zero add one makes one. And the ones digit has to decrease by one. So we need to take away one from nine. And that gives us an answer of 18. One ten and eight ones.
So what will the next answer be, three times nine? Remember, the tens digit increases by one and the ones digit decreases by one. What do you think the answer should be? We added one to the tens to make two. And we took away one from the units to make seven. So three times nine is 27.
Let’s add one to the tens digit, which gives us three. And if we take away one from the ones digit, that will give us six. So four times nine is 36. So to calculate our answer, we wrote out the multiplication facts. And we used the pattern, increased the tens digit by one each time, and decreased the ones digit by one each time. To find our answer, 36. Four times nine is 36.
