Video: Multiplying by 2 Using Repeated Addition Method

What are the two missing numbers in this table?


Video Transcript

What are the two missing numbers in this table?

Can you see where the two missing numbers belong? They’re both in the bottom row, here and here. Now, for us to understand what these two missing numbers might be, we need to understand how this table works. Can you see a clue that might help us? This table is all about multiplying by two. We take a number from the top row, multiply it by two, and then that gives us the number in the bottom row. It’s a little bit like the idea of a multiplying machine, where a number goes in, it gets multiplied by two, and then a different number comes out. This is exactly what’s happening in our table.

Number one on the top row gives us number two on the bottom row. One times two equals two. And number two on the top row gives us four on the bottom row because two times two equals four. So, we can see then that our two missing numbers are going to be what we get when we multiply three by two and what happens when we multiply six by two.

Now, we could think about each of these facts completely separately. We could think about three times two and then six times two. But these two facts are linked. Can you see what the link is between three and six? We know that if we double three, we’d get six. So, do you think if we double the answer to three times two, we might find the answer to six times two? Let’s see whether multiplications work like this.

Three times two is worth two, four, six. So, we know that our first missing number is six. Can you predict what our second missing number’s going to be? We can take the answer for three times two and then double it. And six doubled is 12. Let’s count in twos and see whether the number 12 fits in the pattern. Two, four, six, eight, 10, 12. It worked!

We multiplied three by two to find our first missing number. And we knew that we could double the answer to three times two to find the answer to six times two. This gave us our second missing number. Three times two is six. And six times two is 12. Our two missing numbers are six and 12.

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