Timelines are the most familiar modify of lines with numbers, so let's begin from there. Here is an example of a timeline.

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8 am 9 am 10 am 11 am 12 pm 1pm 2 pm 3 pm 4 pm 5 pm

Timelines show divisions of instance that crapper be large or small. They ofttimes hit coequal divisions for a certain span of time. Depending on the timeline, the spacing might be by days, months, years, decades, centuries, or any other period of time. But whatever the division, it's usually the same throughout the whole line. However, if this doesn't suit the purpose, the divisions crapper be as large or as small as serves the need.

No concern what period of instance is covered on timelines, the lowest drawing (the earliest years) are always toward the left and the higher drawing (the later years) are always towards the right. Also, timelines crapper be as daylong or as short as fits the need. They move and stop wherever you like.

Number Lines and Time Lines

Number lines are like timelines that hit coequal divisions. They also hit lower drawing towards the left and higher drawing towards the right. But they hit some differences as well.

? Timelines crapper be flat or vertical; sort lines are virtually always shown as horizontal.

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? Number lines go on forever. Unlike timelines, sort lines are infinite. This is symbolized by their existence worn with an mark on apiece modify like this:

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? Number lines hit a central mark that must always be there: 0 (zero).

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0

To the correct of the zero are the constructive integers. They do not hit to be marked as positive: they're understood to be positive. To the left of the zero are the perverse integers. They are apiece marked with a minus sign, like this:

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-3 -2 -1 0 1 2 3 4

To some grouping this may countenance fantastic and unfamiliar. If you are digit of them, just imagine a weather thermometer: it is does not go on forever, it's true, and it's oriented vertically. But still, it has the constructive and perverse drawing and zero.

What Number Lines Are Good For

Because many grouping hit travail with the construct of adding and subtracting a perverse drawing or a intermixture of constructive and perverse numbers, sort lines crapper be highly multipurpose in helping them visualize the process. You crapper conceive most it like this:

* If both drawing are constructive or zero and are existence added, you crapper begin with either digit and count to the right. For example: 1 + 2 = Start at 1 and count 2 to the right, and you intend 3.

* If both drawing are perverse and are existence added, you crapper begin with either digit and count to the left. For example: -1 + (-2) = Start at -1 and count 2 to the left, and you intend -3.

* If both drawing are constructive and digit is existence deducted from the other, move with the prototypal digit and count to the left. For example 1 - 2 = Start at 1 and count 2 to the left, and you intend -1.

* If both drawing are perverse and digit is existence deducted from the other, move with the prototypal digit and count to the right. For example -2 - (-3) Start at -2 and count 3 to the right, and you intend 1.