WEBVTT
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Calculate 13 minus four.
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In the black box, we have 13 blocks.
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We have one block of 10 and three blocks of ones, 13.
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Letâ€™s try to take away four of the blocks: one, two, three, but now we have a problem.
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We have taken three blocks away from the thirteen, and there is now one block of 10 inside our box.
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How do we take one away from this block of 10?
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We have to turn this block of 10 into ones.
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Instead of having one large block of 10, we need 10 small blocks, like this.
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Now that we have 10 small blocks, we can take one more block away.
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Now we have nine blocks in the box.
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If you take four away from 13, you get nine.
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13 minus four equals nine.