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Secondary 2 · Mathematics
Numbers · Integers

Representing Integers on the Number Line

Before you start, make sure you know: Representing Integers on the Number Line (Secondary Year 1 (first cycle))
Before you start, make sure you know: Operations with Integers (Secondary Year 1 (first cycle))

Yaritza rides the cable car in Puerto Plata up to the top of Isabel de Torres, and Wilkin goes down in a tourist submarine to explore the sea floor. If sea level is $0$, how do you place both of them on the same number line? And how far apart are they? In this section you will figure it out.

Representar enteros en la recta

On the number line, $0$ is the origin. Positive numbers go to the right and negative numbers go to the left. Between one mark and the next there is always the same distance: one unit.

Opposite numbers (like $-4$ and $+4$) are the same distance from the origin, one on each side.

Number line showing that the opposite numbers −4 and +4 are the same distance, 4 units, from the origin. −4 0 +4 same distance from 0: are opposites 4 4

A number is to the left of another when it is smaller. So, to order numbers from least to greatest, just read the number line from left to right: $-6 < -3 < -1 < 2 < 4$.

You can also represent movements with arrows: moving right means adding, and moving left means subtracting.

Practice★☆☆Not started
Draw a number line in your notebook and represent the following integers on it: $$-4, \quad +3, \quad 0, \quad -1, \quad +5$$ You can do it on paper and send a photo…

Draw a number line in your notebook and represent the following integers on it:

$$-4, \quad +3, \quad 0, \quad -1, \quad +5$$

You can do it on paper and send a photo with your answer.

Solve
Practice★☆☆Not started
Place the following numbers on the number line and use it to order them from least to greatest using the symbol $<$: $$-6, \quad +2, \quad -3, \quad +4, \quad -1$$

Place the following numbers on the number line and use it to order them from least to greatest using the symbol $<$:

$$-6, \quad +2, \quad -3, \quad +4, \quad -1$$
Solve
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Represent the number $-3$ and its opposite on the number line. How far is each one from the origin? You can use this number line, in which the origin and the units are…

Represent the number $-3$ and its opposite on the number line. How far is each one from the origin?

You can use this number line, in which the origin and the units are marked (each mark is one unit), or draw your own:

Number line with unit marks from -5 to 5, with the origin 0 and the 1 labeled 0 1

You can do it on paper and send a photo with your answer.

Solve

Movimientos y temperaturas

The number line is useful for following a trip step by step. Each movement is an arrow that starts where the previous one ended. You can also draw it vertically, like a thermometer.

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A thermometer shows a temperature of $4^\circ\text{C}$ at ten in the morning. If at eight in the evening the temperature has dropped by $6^\circ\text{C}$, represent both…

A thermometer shows a temperature of $4^\circ\text{C}$ at ten in the morning. If at eight in the evening the temperature has dropped by $6^\circ\text{C}$, represent both temperatures on a line and indicate the final temperature.

Solve
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A scuba diver is at a depth of $8$ meters below sea level. If they decide to go up $3$ meters to look at some fish, what depth are they at now? Represent the movement…

A scuba diver is at a depth of $8$ meters below sea level. If they decide to go up $3$ meters to look at some fish, what depth are they at now? Represent the movement using arrows on a horizontal number line.

Sea level ← Depth (-) Surface (+) −8 0 Start
Solve
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A food delivery driver begins his shift at "Point Zero" on a main avenue. He makes the following journeys: 1. Travels $4$ kilometers to the east ($+4$). 2. From there,…

A food delivery driver begins his shift at "Point Zero" on a main avenue. He makes the following journeys:

  1. Travels $4$ kilometers to the east ($+4$).

  2. From there, travels $7$ kilometers to the west.

  3. Finally, travels another $2$ kilometers to the west to deliver his last order.

Draw a number line in your notebook, represent each movement using arrows, and determine which kilometer mark he is at when finished.

−6 −5 −4 −3 −2 −1 0 1 2 3 4 5 6 Start +4 km −7 km −2 km
Solve

Leer y ordenar con opuestos y valor absoluto

To locate $-a$ (the opposite of $a$), reflect $a$ to the other side of zero. The absolute value $|a|$ is the distance from $a$ to the origin, so it is never negative: $|-5| = 5$.

When you are given expressions like "the opposite of $3$" or "the absolute value of $-5$," first calculate their value and then place it on the number line.

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On the following number line, four points represented by letters have been marked. Identify which integer corresponds to each of the letters $A$, $B$, $C$, and $D$.

On the following number line, four points represented by letters have been marked. Identify which integer corresponds to each of the letters $A$, $B$, $C$, and $D$.

0 A B C D
Solve
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Draw a number line and place the following elements on it. Then, order them from least to greatest using the symbol $<$: The number $-4$. The opposite of $3$. The…

Draw a number line and place the following elements on it. Then, order them from least to greatest using the symbol $<$:

  • The number $-4$.

  • The opposite of $3$.

  • The absolute value of $-5$.

  • The number $0$.

  • The opposite of the opposite of $-2$.

You can do it on paper and send a photo with your answer.

Solve
Practice★★☆Not started
Represent the number $-3$ and all the integers whose absolute value is less than it on the number line. Is it possible to complete this task? Justify your answer based…

Represent the number $-3$ and all the integers whose absolute value is less than it on the number line. Is it possible to complete this task? Justify your answer based on the definition of absolute value and its graphical representation.

You can do it on paper and send a photo with your answer.

Solve

Distancia entre dos puntos

Number line illustrating the distance between two integers as the length of the segment between them. −6 0 +3 distance = 6 + 3 = 9 6 3

If the two points are on opposite sides of zero, you add their distances from the origin. If they are on the same side, you subtract. Both situations are summed up in a single rule.

The midpoint between $a$ and $b$ is the same distance from both: it is $\dfrac{a+b}{2}$. For example, between $-7$ and $+3$ it is $\dfrac{-7+3}{2} = -2$, which is $5$ units from each.

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In a ski resort in Sierra Nevada, the thermometer recorded the following temperatures throughout the morning: At 8:00: $-6$ $^\circ$C At 10:00: $-2$ $^\circ$C At 12:00:…

In a ski resort in Sierra Nevada, the thermometer recorded the following temperatures throughout the morning:

  • At 8:00: $-6$ $^\circ$C

  • At 10:00: $-2$ $^\circ$C

  • At 12:00: $+3$ $^\circ$C

  1. a) Represent the three temperatures on a vertical number line (like a thermometer).
  2. b) What was the temperature change (distance on the line) between 8:00 and 12:00?
Solve
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Find the integer that is exactly the same distance from $-7$ and from $+3$ on the number line. In the figure those two numbers are marked. Represent it graphically on…

Find the integer that is exactly the same distance from $-7$ and from $+3$ on the number line. In the figure those two numbers are marked. Represent it graphically on the line to check your result and explain how you calculated it.

Number line with the integers from −7 to 3, with the points −7 and 3 marked in blue−6−5−4−3−2−1012−73
Solve
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A submarine and a rescue helicopter are positioned on the same vertical line. If we transpose their positions to a horizontal number line where $0$ is sea level: The…

A submarine and a rescue helicopter are positioned on the same vertical line. If we transpose their positions to a horizontal number line where $0$ is sea level:

  • The submarine is located at point $S$.

  • The helicopter is located at point $H$.

  • It is known that $|S| = |H| - 200$.

  • The distance between the submarine and the helicopter is $500$ meters.

Draw the number line and find the coordinates of $S$ and $H$, knowing that the helicopter flies above sea level and the submarine is submerged.

|H| |S| |S| 200 m 0 Sea level S |S| H 500 m Submarine (-) Helicopter (+)
Solve

Intervalos: extremos abiertos y cerrados

A condition like $-2 < x \le 3$ describes, all at once, all the integers in a stretch of the number line, not just one.

Number line with the interval from −2 (open circle, excluded) to +3 (filled circle, included). −3 −2 −1 0 1 2 +3 4 −2 not included +3 included length 5

In interval notation, $-2 < x \le 3$ is written $(-2, 3]$: a parenthesis if the endpoint is not included, a bracket if it is included.

Practice★☆☆Not started
Write in your notebook all the integers $x$ that satisfy the condition $-2 < x \leq 3$ and represent them on the number line. Pay close attention to the open and closed…

Write in your notebook all the integers $x$ that satisfy the condition $-2 < x \leq 3$ and represent them on the number line. Pay close attention to the open and closed endpoints.

You can copy this number line into your notebook:

Empty number line with the integer marks from −4 to 4−4−3−2−101234
Solve
Practice★★☆Not started
Write down all the integers $x$ that satisfy the following two conditions simultaneously and represent them on a number line: $-5 < x \leq 2$ The absolute value of $x$…

Write down all the integers $x$ that satisfy the following two conditions simultaneously and represent them on a number line:

  • $-5 < x \leq 2$

  • The absolute value of $x$ is greater than $1$, that is, $|x| > 1$.

Solve
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Identify all the integers $n$ that satisfy the following three conditions simultaneously and plot them on a number line: 1. The absolute value of $n$ is less than or…

Identify all the integers $n$ that satisfy the following three conditions simultaneously and plot them on a number line:

  1. The absolute value of $n$ is less than or equal to $7$: $|n| \leq 7$.

  2. $n$ is strictly greater than its opposite: $n > -n$.

  3. The distance between $n$ and the number $-2$ is greater than $5$ units.

Solve

Valor absoluto en la recta

The equation $|x| = 4$ has two solutions: the two points that are at distance $4$ from $0$.

Number line with the two solution points, −4 and +4, located at distance 4 from the origin. −4 0 +4 same distance from 0 d d

With $|x - c| = d$ the same thing happens, but the center is $c$ instead of $0$: $x$ is $d$ units from $c$, to the right or to the left.

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Represent on the number line all the integers whose absolute value is equal to $4$. How many numbers have you marked? You can do it on paper and send a photo with your…

Represent on the number line all the integers whose absolute value is equal to $4$. How many numbers have you marked?

You can do it on paper and send a photo with your answer.

Solve
Practice★★☆Not started
Given the integers $x$ whose distance from the origin ($0$) is $6$ units, and using the number line in the figure (or drawing an identical one in your notebook): a)…

Given the integers $x$ whose distance from the origin ($0$) is $6$ units, and using the number line in the figure (or drawing an identical one in your notebook):

  1. a) Represent those numbers on the number line.
  1. b) Also represent their opposites.
  1. c) What do you notice about the position of the original numbers and their opposites on the line?
Number line graduated from −8 to 8 with the origin marked−8−7−6−5−4−3−2−1012345678
Solve
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Given the following expressions, plot on the number line the values of $x$ that make them true: a) $|x - 3| = 5$ b) $|x + 2| = 4$ Which integer is a solution to both…

Given the following expressions, plot on the number line the values of $x$ that make them true:

  1. a) $|x - 3| = 5$
  2. b) $|x + 2| = 4$

Which integer is a solution to both expressions at the same time? Mark it in a different color on your number line.

−8 −7 −6 −5 −4 −3 −2 −1 0 1 2 3 4 5 6 7 8 9 10 a) |x - 3| = 5 center = 3 distance = 5 distance = 5 b) |x + 2| = 4 center = −2 distance = 4 distance = 4
Solve

Problemas con condiciones sobre la recta

In hard problems you are given clues about positions, distances, and absolute values. The strategy is always the same: draw the number line, translate each clue into a condition, and check whether there are two possibilities (one on each side of zero).

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An explorer is in a network of underground caves represented on a horizontal number line. The origin $0$ is the cave entrance. We know that the explorer has made the…

An explorer is in a network of underground caves represented on a horizontal number line. The origin $0$ is the cave entrance. We know that the explorer has made the following successive movements:

  1. Starts at an unknown point $x$.

  2. Moves forward $+12$ units.

  3. Moves back twice their initial position $x$ (that is, $2x$ units to the left).

  4. Moves forward the opposite of $-5$.

If they finally end up at point $-3$, represent the situation on the number line (draw the line and the movements yourself) and determine, with reasoning, the value of the starting point $x$.

Solve
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On the number line of integers, point $A$ represents the number $-4$. Point $B$ is a number such that its distance from the origin is three times the distance of $A$…

On the number line of integers, point $A$ represents the number $-4$. Point $B$ is a number such that its distance from the origin is three times the distance of $A$ from the origin. If point $C$ is the midpoint of the line segment formed by the opposite points of $A$ and $B$, which numbers could $C$ represent? Note that there are two possible solutions for $B$. Represent them graphically.

Solve
Practice★★★Not started
Three points $P$, $Q$, and $R$ are located on the number line. It is known that: Point $Q$ is the opposite of $-6$. Point $P$ is at a distance of $10$ units from $Q$, to…

Three points $P$, $Q$, and $R$ are located on the number line. It is known that:

  • Point $Q$ is the opposite of $-6$.

  • Point $P$ is at a distance of $10$ units from $Q$, to the left.

  • Point $R$ satisfies $|R| = |P| + |Q|$.

Calculate the values of $P$, $Q$, and $R$. Represent all possible positions of $R$ on the line and explain which of them is furthest from the midpoint between $P$ and $Q$.

You can do it on paper and send a photo with your answer.

Solve
Practice★★★Not started
Consider a negative integer $a$ and a positive integer $b$. On the number line, the distance between $a$ and $b$ is $15$ units. If the absolute value of $a$ is double…

Consider a negative integer $a$ and a positive integer $b$. On the number line, the distance between $a$ and $b$ is $15$ units. If the absolute value of $a$ is double the absolute value of $b$, that is, $|a| = 2 \times |b|$, find the values of $a$ and $b$ and represent them. What is the opposite of the sum $a + b$?

Solve
Practice★★★Not started
Draw a number line and represent the following sets of numbers so that the difference between them can be seen (for example, by using a different color for each set):…

Draw a number line and represent the following sets of numbers so that the difference between them can be seen (for example, by using a different color for each set):

  • Set $X$: integers $x$ such that $|x| < 4$.

  • Set $Y$: integers $y$ such that their opposite $-y$ is between $-2$ and $5$ (both excluded).

State, with reasoning, which integers belong to both sets at the same time.

You can do it on paper and send a photo with your answer.

Solve

Resumen

Go back to the beginning: with sea level as $0$, Yaritza at the top is at a positive number and Wilkin under the water is at a negative one; the distance between them is $|a - b|$.

See all the exercises in this section