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Count back to find 15 divided by three.
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In this question, we’ve got a division to solve.
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We need to divide 15 by three.
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One way of thinking of this is, how many threes are there in 15?
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And one way we could find out how many threes are in 15 is if we count back, which is what this question tells us to do.
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We could do this on a number line.
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So we could start by sketching a number line and labeling zero at one end and 15 at the other.
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But remember, we’re going to be working backwards, so we’re going to start at 15 and go back toward zero.
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Now to find out how many threes there are in 15, we could count back in threes.
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So starting on 15, let’s count back one lot of three.
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15, 14, 13, 12.
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So we know there’s definitely one lot of three in 15.
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Let’s take away another lot of three, starting with 12, 11, 10, nine, and another jump of three, starting with nine, eight, seven, six.
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So we’ve already made three jumps of three and we’ve landed on the number six.
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Can you see how many more jumps of three we need to make?
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Six, five, four, three.
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And then if we take away one more lot of three, it’s going to take us to zero.
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We’ve made five jumps of three altogether to get from 15 all the way back to zero.
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This tells us that there are five threes in 15.
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We’ve used counting backwards or repeated subtraction to help us solve this division.
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15 divided by three equals five.