Question Video: Multiplying by Nine Using Skip Counting Mathematics • 3rd Grade

Video Transcript

This sequence chart will help us multiply by nine using skip counting by nines up to 10 times. Use skip counting to find nine times two, and then use skip counting to find nine times nine.

In this question, we’re given a picture of a sequence chart. If we look at it carefully, we can see it’s pretty much the same as 100 square. Each row contains 10 numbers, but instead of having 10 rows that go all the way up to 100, we have nine rows and we stop at 90. And the reason why we stop at 90 is that this sequence chart is to help us learn our nine times tables facts. The way it’s been labeled helps us skip count by nines up to 10 times. The number nine, of course, is one less than 10.

To count in tens using a chart like this, we would simply go down a row. Six becomes 16 and then 26. So if that’s how to skip count in tens using a sequence chart like this, to skip count in nines, we could move down a square and then back a square. It’s the same as adding 10, taking away one. And we can see all the multiples of nine have been labeled on this chart. They make quite a clear diagonal pattern, don’t they? In the first part of the question we’re told to use skip counting to find the answer to nine times two, or if we think of the numbers the other way around two times nine or two lots of nine. Let’s do this then.

Starting at nine, we say nine, 18. Nine times two is 18. Next, we need to use the same skip counting method. But this time, we need to count a lot further. We need to count up to nine lots of nine. So we’ll start at nine again and say nine, 18, 27, 36, 45, 54, 63, 72, 81. The whole sequence chart only shows up to 10 times nine, and we’ve said all the numbers apart from one. We’ve skip counted in nines nine times, and we’ve ended on the number 81. There are lots of patterns with a nine times table, and we can see some in this sequence chart. We followed the pattern to skip count by nines to find the answer to two multiplications. Nine times two equals 18, and nine times nine equals 81.