# Question Video: Multiplying by 2 Using Repeated Addition Method Mathematics • 3rd Grade

In multiplying by 2, each row is 2 more than the previous one. 1 × 2 = 2, 2 × 2 = 4, 3 × 2 = 6 Complete the following: 4 × 2 = ＿ Complete the following: 5 × 2 = ＿

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### Video Transcript

In multiplying by two, each row is two more than the previous one. One times two equals two. Two times two equals four. Three times two equals six. Complete the following: Four times two equals what. And then, complete the following: Five times two equals what.

In maths, there are often patterns everywhere we look. And in questions like this, we can use the patterns that we find that help us find the answers. Perhaps one of the best sentences we could ever say in maths is “I don’t know the answer, but I do know this fact, and I’m going to use it to help.” And in a way, this is what this question is all about, using facts that we already know to help us find facts that we don’t.

Our first sentence tells us about a pattern. In multiplying by two, each row is two more than the previous one. In the model, we can see some rows of cubes. And each cube has a value of two. We can see the number two written on them. The first row shows one lot of two. And of course, we know one times two equals two. But then, look what happens in our second row. We’ve taken the answer from before, and we’ve added one more lot of two, the yellow cube on the end. We now have two lots of two. And two times two equals four.

The pattern continues with our third row. This is made up of the answer from before and then two more. We know from the last fact that two times two equals four. So, if we find two more than this, we get the answer six. And that’s how we know three times two equals six. Now, we’ve got some times tables facts to complete. Perhaps you know the answers already. But in case you don’t, let’s continue using this method.

We’ll use facts that we already know, and we’ll build on them. So, the first fact we need to find is four times two. And if we look at our row of cubes, we can see that there are three red cubes. We know where these are from, don’t we? These are the three cubes that made up the answer to the last fact. And just like all our other facts, we’ve got a new cube on the end. These are the two more that we need to add.

We know from our last fact that three times two is six. So, to find four times two, we simply need to add another two. We need to find two more than six. And six plus another two is eight, so four times two must equal eight.

In the last part of the question, we need to find five times two. So, we can do the same thing again. Take the answer from the last question, which is eight, and then add another two. Eight add two equals 10. And so, we know five times two equals 10. Even though we may not have known all the multiplication facts in this question, we took the facts we did know and we used them to help. If we know what three times two is, we simply add two to find four times two. And if we know what four times two is, we do the same again to find five times two. Four times two equals eight. And five times two is 10. Our two missing numbers are eight and 10.