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Each monster has six eyes.
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How many eyes do eight monsters have?
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The first piece of information that we’re told in this problem is that each monster has six eyes.
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There are five on top of the head and one big one in the middle.
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The question then goes on to ask us, how many eyes do eight monsters have?
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And so, we need to use what we know about one monster to help us find the total eyes that eight monsters have altogether.
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Because we’re finding several lots of the same amount, one way to find the answer could be to add six add six add six eight times.
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But there is a quicker way.
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Repeating the same addition lots of times is the same as multiplying.
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There are eight monsters and there are six eyes on each monster.
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So, we’re looking for the total of eight multiplied by six.
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How can we find eight sixes?
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Perhaps you know the multiplication fact already.
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Another method might be to skip-counting in sixes.
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This is similar to adding six over and over again.
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So, there are quicker methods we could use.
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Another method we could use, because we’re multiplying by eight, is to use doubling to help.
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Let’s have a go at using this method.
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The key fact to remember is that when a number is multiplied by eight, it’s doubled, doubled then doubled again.
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Let’s show how this works using our bar model.
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So, we need to multiply six by eight.
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Starting with the number six we double.
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Double six is 12.
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That’s the same as having two lots of six.
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Next, we need to double 12.
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We double the ones to get four and double the tens to get 20, 24.
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We started with six.
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We doubled, and we doubled again.
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That’s the same as finding six times four.
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Now we need to double one more time.
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We can see that by doubling a third time, we’ll be able to find out the total number of eyes that all eight monsters have.
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What’s double 24?
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Double the ones.
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Two lots of four is eight.
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And double the tens.
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Two lots of 20 is 40.
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And so, 24 doubled equals 48.
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So, by using our double-double-double method we were able to multiply six by eight.
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And so, as we look at this row of monsters we can see 48 eyes staring back at us.