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Let’s take a look at how we read and write integers.
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Numbers like eight, negative four, 15, negative 76, and zero are all examples of integers.
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An integer is any number in this set, where the dot dot dots on either side means continues without end.
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The word “integer” comes from the Latin word that means “whole.”
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Another way to say that is that an integer is a number that can be written without any fractional parts.
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Numbers like one-half, one and six-tenths, negative five and four-tenths are not integers; they cannot be written without fractional parts.
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Here’s a number line with some integers marked on it.
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Positive integers are integers that are greater than zero.
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Negative integers are integers that are less than zero.
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Zero is neither positive nor negative.
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Let’s look at some examples of how we use positive and negative integers.
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Parts of New Orleans, Louisiana, sit below sea level by nearly seven feet.
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Write the elevation value as an integer.
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So here’s what we know.
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We know seven feet and we know below sea level.
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We know we’re dealing with seven, but should it be a positive seven or a negative seven?
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If you guess negative seven, you’re right.
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Since we’re dealing with an area that’s below sea level, negative seven is how we represent the elevation of those parts of New Orleans.
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Speaking of sea level, if a place is exactly at sea level, what integer would represent that?
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The answer is zero.
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Anything that’s neither above sea level nor below sea level sits exactly at sea level and would be at an elevation of zero.
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Next up a true or false question, true or false: negative 63 is an integer.
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What do you think?
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It’s true!
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Negative 63 has no fractional parts or components; so it is by definition an integer.
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Is seven and two-tenths an integer?
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Any thoughts?
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Seven and two-tenths is not an integer.
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Another way to write seven and two-tenths would be to have a seven with a fraction of two over ten.
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This fractional piece means we’re not dealing with an integer here.
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Decimal numbers, because they have fractional pieces, are not integers.
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Let’s quickly summarise the words we’ve been using.
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An integer is a number written without fractional parts.
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A positive integer is an integer that is greater than zero.
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And finally, a negative integer is an integer less than zero.