Video Transcript
We can use number lines to multiply. Jump forward in sevens. Make three jumps. What number will you land on? Write an addition sentence matching the number line. Write a multiplication sentence matching the number line.
This question is all about how we can use number lines to help us multiply numbers together. And the way we do that is to make jumps of the same amount again and again. And that’s why we’re told to jump forward in sevens. And we can see in the picture of the number line that above each arrow it says plus seven. Every time, they’re jumps of the same amount.
The first question in this problem asks us for the number that we will land on. So, let’s start on zero and jump forward in sevens three times. And we’ll see where we end up. Zero plus seven equals seven. That number is already completed on the number line. Let’s make a second jump of seven. Seven plus seven equals 14, seven, eight, nine, 10, 11, 12, 13, 14. So, we’ve now added two lots of seven. Let’s jump forward one more lot of seven. 14 plus seven equals 21, 14, 15, 16, 17, 18, 19, 20, 21. So, the number that we will land on is 21.
Our next question asks us to write an addition sentence that matches the number line. We jumped forward in sevens three times. How can we write this as an addition? Seven plus another seven plus another seven. And what did it equal? 21. Seven plus seven plus seven equals 21.
Finally, we’re asked to write a multiplication sentence matching the number line. Because by adding the same number again and again, what we’ve really been doing is multiplying. We counted three lots of seven, and if we look at the array that we drew to help us count on, we have three rows of seven, or three groups of seven. Our multiplication sentence should show three lots of seven. Three times seven equals 21.
So, if we’re making the same jump each time, we can add the same number lots of times, or we can multiply to find the same answer. We jumped forward in sevens, and we made three jumps. The number that we landed on was 21. The addition sentence that matches the number line is seven plus seven plus seven equals 21. And then, the multiplication sentence that matches the number line is three times seven equals 21.
