Question Video: How to Model Multiplication by 8 Using Skip Counting Mathematics • 3rd Grade

The sequence chart can help us multiply by 8 using skip counting by eights up to 10 times. Use skip counting to find 8 × 2. Use skip counting to find 8 × 9.

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Video Transcript

The sequence chart can help us multiply by eight using skip counting by eights up to 10 times. Use skip counting to find eight times two. And then use skip counting to find eight times nine.

In the picture, we can see what’s described as a sequence chart. It’s a little bit like 100 square, except it’s not a square and it doesn’t go all the way to 100. But it does show all the numbers from one to 80. And if we look closely, we can see that some of the numbers have been written in blue. The numbers eight and then 16, 24, 32. These are all numbers in the eight times table. And because these numbers have been written in a different color, they can help us to skip count by eight. Look how they make a pattern on the chart. To get to the next number, we go down a row and then back two squares, down a row, back two. And if we think about it, we know why this is, don’t we?

Skip counting by eight is the same as adding eight each time. And eight is two less than 10. When we move down a row on a chart like this, it’s the same as adding 10. And then when we move back two squares, this is the same as taking away two. Add 10, take away two; add 10, take away two. That’s why these numbers in the eight times table show this pattern. And if we continue the sequence, we can see all the numbers in the eight times table up to 10 times eight, which is 80.

In the first part of the question, we’re asked to use skip counting to find eight times two. Now, it might sound like this is a two times table fact, not an eight times table fact, eight lots of two. But we know we can read multiplication facts like this with the numbers in the opposite order, and it’ll still give the same answer. So, eight times two is exactly the same as two times eight. To find the answer, we need to count in eights twice. Let’s use the sequence chart to help. Eight, 16. Eight times two equals 16.

In the second part of the question, we need to count a little further. We’re asked to use skip counting to find eight times nine. And again, we know that eight times nine is the same as nine times eight or nine lots of eight. So, let’s use our sequence chart to count in eights nine times. Eight, 16, 24, 32, 40, 48, 56, 64, 72. We skip counted by eight nine times. And we reached the number 72. And so, we know that eight times nine or nine times eight equals 72. In this question, we found the answer to two multiplication facts by using this sequence chart. We skip counted by eights. Eight times two equals 16, and eight times nine equals 72.

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