Question Video: Understanding That Repeated Addition Is the Same as Multiplication Mathematics • 3rd Grade

Multiplication is the same as repeated addition, but quicker. Select a multiplication equation which matches the repeated addition sentence 42 + 42 + 42 + 42 + 42 + 42 = 252.

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Video Transcript

Multiplication is the same as repeated addition, but quicker. Select a multiplication equation which matches the repeated addition sentence. And then, we’re given the repeated addition sentence 42 plus 42 plus 42 plus 42 plus 42 plus 42 equals 252.

You can hear by the way we said that sentence. There are lots of 42 being added again and again. This is repeated addition. And as the problem says, instead of adding the same number again and again, we can multiply instead. Instead of multiple addition, we can use multiplication. So, in this problem, we’re given a long addition sentence, and we’re given five possible multiplications that we could use instead. Which one can we use?

Let’s start by looking at the addition sentence. How many lots of 42 are we adding? One, two, three, four, five, six, there are six lots of 42. Let’s write that phrase down to help us. So, we’re looking for a multiplication that gives us six lots of 42. Which one can we use? Well, if we look carefully, there are only two multiplications that might show six lots of 42.

There’s this one which repeats the number 42 six times but multiplies them together, 42 multiplied by 42 multiplied by 42, and so on. And there’s this one which tells us the 42 multiplied by six equals 252. How many lots of 42 are in the first of these sentences? Remember, we’re looking for six lots of 42.

Well, if we multiply the first two numbers together, we’ve got 42 lots of 42. We can see that this number is multiplied by 42 again, and again, and again, and again. The answer will be really large. So, although it may look like we’ve got six lots of 42 in this multiplication, when we think about what these symbols mean, we realize we have a lot more than six lots of 42.

Let’s look at our second possible multiplication. 42 multiplied by six, does this show six lots of 42? We know that with multiplication, we can swap the numbers around and still get the same answer. So, 42 multiplied by six is the same as six multiplied by 42, or six lots of 42. And so, instead of adding 42 six times, we can simply work out the multiplication 42 times six equals 252.

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