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Dependent & independent variables

Identifying the dependent and the independent variables in a word problem. Created by Sal Khan.

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  • leaf green style avatar for user Legolas Greenleaf
    So in a nutshell, is the dependent variable the variable that is determined by the variable on the other side of the equation, like for example, r = p(6), the r would be the dependent variable. Do I have the right idea?
    (15 votes)
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    • duskpin ultimate style avatar for user Taly
      Also the equation has no "other side" equation mean something = something. 1+1=2 and 2=1+1
      the whole (2=1+1) is called an equation. Trust me you should not take these simple words for granted. 90% of the solution is understanding the question.
      (4 votes)
  • aqualine ultimate style avatar for user manuel.amaya
    I still don't get it whats the difference between independent and dependent
    (7 votes)
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    • primosaur ultimate style avatar for user avisarus
      The dependent variable is supposed to DEPEND on the independent variable.
      If I do make a plot to show how much water I drink depending on what the temperature is outside. The # of cups of water is the dependent variable. This leaves the independent variable to be the temperature!

      You can also tell if it's the other way around. Does the temperature outside depend on how much water you drink? No, no it doesn't! Tip for the future, if it does seem to make sense both ways then you might have a junk design for your experiment.
      (20 votes)
  • duskpin sapling style avatar for user Theguywhoisbob
    Can someone please help me understand the basics because The video goes to fast and please vote this because i'm trying to get achevements I will like all of yours.
    (7 votes)
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    • duskpin ultimate style avatar for user emhametz
      Assuming you're asking about independent and dependent variables. The independent variable is the variable being controlled in the problem, and the dependent variable is the variable that changes because of this control. For instance, if you were to be measuring the number of miles you drove in any number of hours at a constant speed, the controlled independent variable is the time in hours and the dependent variable is the distance you drove in miles.
      (5 votes)
  • leafers seedling style avatar for user 21oovermiller
    Which is the dependent variable? Is it the total or not?
    (5 votes)
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    • leaf blue style avatar for user Stefen
      The dependent variable is the one that depends on the value of some other number.
      If, say, y = x+3, then the value y can have depends on what the value of x is.
      Another way to put it is the dependent variable is the output value and the independent variable is the input value. So for y=x+3, when you input x=2, the output is y = 5.
      (8 votes)
  • starky ultimate style avatar for user LearningFun
    How come the world uses Dependent and independent varible not only in math but in science to? Do they mean the same thing or what?
    (4 votes)
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    • starky tree style avatar for user Ida Fan
      You're right! In both math and science, we need a word to describe a variable that changes as something else changes (dependent ) and a variable that does not change as a result of something else changing, and instead causes something else to change (independent).
      (9 votes)
  • blobby green style avatar for user 25ad46
    What is an indipendent varible
    (5 votes)
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    • orange juice squid orange style avatar for user Ayva Dunn
      The independent variable is the variable that changes the dependent variable. So, say if you drink water from a large water bottle, the amount of liters you drink depends on how many times you drink from your water bottle. If you drink different amounts of water from the bottle, you will have a different amount of liters you drank
      (4 votes)
  • blobby green style avatar for user a a
    In a y=mx+b equation, which one is dependent?
    (6 votes)
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  • aqualine ultimate style avatar for user Dabstab
    what if the problem has 4,000,000 variables??
    (2 votes)
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  • leaf red style avatar for user Reggae
    I don't understand how you find out the dependent variable and the independent variable. P
    (4 votes)
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    • primosaur ultimate style avatar for user Anthony Fritz
      The dependent variable is usually graphed on the y-axis, and the independent variable is usually graphed on the x-axis. In addition, the value of the independent variable determines the value of the dependent variable and is used in experiments to test the value of the dependent variable.

      For example, if I were studying the influence of hours studied on the final grade received in a course, the number of hours (the input that changes the output) would be the independent variable and graphed on the x-axis, and the final grade received (the output of number of hours studied) would be the dependent variable and graphed on the y-axis.
      (3 votes)
  • blobby green style avatar for user Kyla Geisha Camille Azuelo
    can u explain what is the dependent and independent of this following variables?
    1. the amount of nitrogen in the soil
    2. the amount of phosphorus in the soil
    3. the amount of rainfall
    4. the amount of potassium in the ground
    5. frequency of weeding
    6. temperature
    (3 votes)
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    • mr pink green style avatar for user David Severin
      You do not have a comparison of two things, which you need to have a independent/dependent relationship. Any of these could be compared over time.
      So if you have the amount of nitrogen in the soil over a given time period or rainfall per month over a year, or temperature from 4 am to 8 pm, these would all be the dependent variable with time as the independent variable.
      (3 votes)

Video transcript

On your math quiz, you earn 5 points for each question that you answer correctly. In the table above, q represents the number of questions that you answer correctly on your math quiz, and p represents the total number of points that you score on your quiz. The relationship between these two variables can be expressed by the following equation-- p is equal to 5q, where p is the points you get and q is the number of questions you answered correctly. And you could see that in the table. If q is 0, if you got no questions right, you get 0 points. If you got no questions right, well, 5 times 0 is going to be 0. If you get one question right, well, 1 times 5 is 5. You get 5 points per question. Two questions right, well, 2 times 5 is 10. 3 times 5 is 15. So this all makes sense. So then they ask us, which of the following statements are true? Check all that apply. So let's think about this. They say the dependent variable is the number of points you score. So when you think about what's happening here, is your number of points you score is being driven by how many questions you get right. It's not like somehow the teacher says you got 15 points and now you have to get exactly three questions right. It's the other way around. The number of questions you get right is the independent variable, and that's driving the number of points you score. So the number of points you score is the dependent variable. And typically, the convention is to have the dependent variable be equal to some expression involving the independent variable. And you see that right over here. p is dependent on what happens to q. Depending on the number of questions, you multiply it by 5, and you get p. So the dependent variable is the number of points you score. The dependent variable is the number of questions you answer correctly. No, we've already talked about that. That's the independent variable. The independent variable is the number of points you score. No, that's not right. That's the dependent variable. The independent variable is a number of questions you answer correctly. Well, that's right. That's what's driving the dependent variable. And we can check our answer.