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Making 17, 18, and 19
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In this lesson, we’re going to learn how to decompose or split up the numbers 17, 18, and 19.
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And we’re going to split them up into 10 ones and also some remaining ones.
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Now, let’s imagine for a moment that these birds have laid 17 eggs altogether.
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We know that one way to show the number 17 is to write the digit one followed by the digit seven.
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Another way is to write the number as a word, but how can we make the number 17?
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What does 17 eggs look like?
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One, two, three, four, five, six, seven, eight, nine, 10.
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We’ve already got 10 ones, but we can see that the number 17 is going to be made up of 10 ones and also some remaining ones.
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Let’s arrange our 10 ones into a ten frame to make them easier to count.
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There we go, 10 ones.
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Let’s keep counting.
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11, 12, 13, 14, 15, 16, 17.
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We can make the number 17 out of 10 ones and seven more ones.
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We could use a part–whole model to show how we can decompose or split up the number 17.
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The whole amount is 17.
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And we can split this up into 10 ones, which is worth 10, and seven ones, which is worth seven.
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10 and seven go together to make 17.
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10 plus seven equals 17.
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Now what if these birds laid one more egg?
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We still have a group of 10 ones.
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But now we have eight more ones instead of seven more ones.
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10 ones plus eight more ones makes 18.
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So just like 10 and seven make 17, 10 plus eight equals 18.
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Now, what about the number 19?
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Well, we’re going to have to sketch another egg.
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We can split up the number 19 into 10 ones and, this time, nine more ones because 10 plus nine equals 19.
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Let’s have a go at answering some questions now where we have to make the numbers 17, 18, and 19.
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Pick the set of cards that shows 18 hearts.
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Now, when we’re talking about the number of hearts that’re drawn on each of these cards, we’re talking about the large hearts in the middle.
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The A on this card stands for the word ace.
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Even if you don’t know what the word ace means, we can work it out by looking at the number of hearts in the middle.
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And an ace stands for the number one.
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It’s worth one.
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So our first set of cards have a value of one and eight.
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Now, we’re looking for a set of cards that shows 18 hearts.
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And we do write the number 18 by writing a one and an eight next to each other.
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So does this mean we can see 18 hearts in the first set?
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No, if we add one and eight together, we get a total of nine.
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We can see nine hearts in the first set.
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This can’t be right.
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Our second set of cards shows one, then another card with one heart on it, and then a card with eight hearts on it.
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Does one, one, and eight make 18?
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Well, as we’ve already said, one and eight go together to make nine.
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And if we add the other heart, we have a total of 10 hearts altogether, not 18.
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Our last set of cards shows the number 10 and eight.
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And we know that 10 ones plus another eight ones gives us a total of 18 ones.
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This set of cards must be the one that shows 18 hearts.
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We know that the first card shows 10 hearts, so let’s treat this as a group of 10 ones and start counting from there.
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11, 12, 13, 14, 15, 16, 17, 18.
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The set of cards that show 18 hearts is the one that contains a group of 10 hearts and then a group of eight hearts.
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Michael had seventeen buttons.
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Pile A had 10 ones.
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How many are in pile B?
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The first important piece of information that we’re given in this problem is that Michael had seventeen buttons.
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Let’s remind ourselves how to write the number seventeen using digits.
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We write the digit one followed by the digit seven.
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And the picture underneath shows us one way that we could split up the number 17 because Michael split up his 17 buttons into pile A, which contains 10 buttons.
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We know this because we’re told underneath pile A had 10 ones.
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And we can also see that the pile is labeled 10 ones too.
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But we’ve also got a second pile, pile B.
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And we don’t know how many ones are in this pile.
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We need to work it out.
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In fact, the question asks us, how many are in pile B?
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In other words, if we are going to split up the number 17 and one of the parts is worth 10 ones, what’s the other part going to be worth?
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You may already know the answer.
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What goes with 10 ones to make 17?
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But let’s start with 10 ones and count on until we get to 17 and see how many ones this is.
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10, 11, 12, 13, 14, 15, 16, 17.
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We can see that 10 ones and seven more ones go together to make 17.
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We could also complete our part–whole model to show that we can split up the number 17 into 10 and seven.
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And because we know that 10 ones and seven more ones go together to make 17, we can say that the number of buttons in pile B is seven.
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Anthony made a train of 19 cubes.
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Which train has been correctly decomposed into 10 ones and some more ones?
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To begin with, we’re told that Anthony made a train of 19 cubes.
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Now, if we ignore the colors for a moment, a train of 19 cubes might look something like this.
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But the pictures that we can see in the question don’t look like a train of cubes at all.
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Well, if we carry on reading the question, we can see what’s happened to Anthony’s train.
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It’s been decomposed.
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This is a long word in maths, but it means something very simple.
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It just means “split up.”
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So Anthony has taken his train of 19 cubes, and he split it up into 10 ones and some more ones.
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Which of the three pictures shows a train that’s been split up into 10 ones and some more ones?
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Let’s start off by thinking about what might happen if we split a number up into 10 ones and some more ones.
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Of course, the number we’re thinking of is the number 19.
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So here’s our group of 10 ones.
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Now, how many ones do we have remaining?
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We have one, two, three, four, five, six, seven, eight, nine ones.
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10 ones plus nine more ones make 19.
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Now, let’s imagine that Anthony breaks apart or splits up his train into 10 ones and nine more ones.
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Which picture shows this?
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Well, we know it’s not going to be the first picture, is it?
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There are lots more cubes there than we need.
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But what about our second picture?
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This shows a group of 10 cubes.
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And we don’t need to count the second group because it’s one less than 10 we can see.
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It must be showing nine cubes.
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And because we know that 10 ones and nine more ones go together to make 19, we know the picture that shows Anthony’s train that’s being split up is the one that shows 10 ones and nine more ones.
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What have we learned in this video?
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Well, we’ve learned how to decompose or split up the numbers 17, 18, and 19 into 10 ones and some remaining ones.