Graph & Equation
Graphing Equation Lessons

Slope of a line

Practice

Now , let's try some MCQ questions to understand this lesson better.
You can start by going through the series of the graphing linear equations questions below

Question 1 on using a linear equation to calculate y-coordinates

Question 2 on the basics of graphing linear equations

Lesson Objective

Learn how to calculate the slope of a line.

About this lesson

A straight line has several properties that you can measure or calculate. One of the property is the slope. In this lesson, you will learn how to formulate and calculate the slope of a line. Note that, the slope is also known as the gradient.

Video : Change in x and y Video : Calculating the slope of a line

What is in this video ?

Change in X and Y
  • 00:00:02.130
    This lesson will explains to you on how to calculate the 'change in x' and 'change in y'.
  • 00:00:10.240
    When you do the calculation, it is important to first run, and then climb. What does this means?. The following example will explain it.
  • 00:00:24.150
    Imagine, that you are at this point right over here with x-coordinate of 2. Now, you run towards the right, notice that your x-coordinate increases..
  • 00:00:37.080
    Now, you see that your current x-coordinate is 5. You can calculate the change in x, by taking the current x-coordinate, 5, minus the original x-coordinate, 2. This gives the change of x of 3
  • 00:00:56.110
    Now, let's take a look at the change in y. You are currently at this point with y-coordinate of 2. When, you climb up from here, your y-coordinate increases. (Increase y-coordinate from 2 to 5).
  • 00:01:11.020
    You see that now, your y coordinate is 4. You can calculate the change in y, by taking the current y-coordinate, 4, minus the original y-coordinate, 2. This gives the change of y of 2.
  • 00:01:28.170
    Alright, for this example, you have the 'change of x' equals to 3, and 'change of y' equals to 2 . Let's take a look at another example.
  • 00:01:43.130
    Imagine, that you are at this point right over here with x-coordinate of 3. When you run towards the left, your x-coordinate decreases.
  • 00:01:57.230
    Now, you see that your current x-coordinate is negative 2. You can calculate the change in x, by taking the current x-coordinate, negative 2, minus the original x-coordinate, 3. This gives the change of x of negative 5.
  • 00:02:17.050
    Now, let's take a look in change in y. When you climb up from here, your y-coordinate increases. (Increase y-coordinate from -4 to 2).
  • 00:02:31.010
    You see that your current y coordinate is 2. You can calculate the change in y, by taking the current y-coordinate, 2, minus the original y-coordinate, negative 4. This gives the change of y of 6.
  • 00:02:48.240
    Alright, for this example, you have the 'change of x' equals to negative 5, and 'change of y' equals to 6 .
  • 00:02:58.020
    With these two examples, you should be able to calculate the 'change in x' and 'change in y.' That is all for this lesson. The next lesson explains the slope of a line.

Calculating the slope of a line
  • 00:00:02.120
    After the lesson on graphing, it is time to learn about the slope of a line.
  • 00:00:12.190
    If we were to put 2 points here, you will see that we can draw a line through these points.
  • 00:00:19.200
    As obvious as it seems, notice that if i move the point up, the line changes.
  • 00:00:26.170
    If you were to observe carefully, one of the things that changes here is the slope of the line. The slope of this line increases further when I move this point up.
  • 00:00:38.070
    Now that you know this, the next question is can the slope be assigned a meaningful number? The answer is yes. But, how do we do it?
  • 00:00:51.110
    With some thought, the most logical way to do this is to take the ratio of the 'change in y' and 'change in x'.
  • 00:01:01.180
    As an example, let's imagine that, you run from this point from here to here. In this case,the change in x is 2. When you climb from here to the point above, the change in y will be equals to 3. So, the slope for this case is 3.0 divided by 2.0, which is 1.5.
  • 00:01:29.030
    Getting a clearer picture of the slope now? Let's look at the 'change in x' and 'change in y' in more detail.
  • 00:01:37.150
    Let me show you the x-coordinates of these points. When you run from here to here. The change in x is 4.0 minus 2.0 which equals to 2.0. Or, simply looking at the grid, 1, 2.
  • 00:01:56.210
    For change in y, let me show you the y-coordinates first. When you climb from here to here, the 'change in y' in this case is 5.0 minus 2.0 which is equals to 3.0. Or, simply looking at the grid, 1 , 2 , 3.
  • 00:02:20.100
    Let's explore further, see what happens when i move this point around.
  • 00:02:25.180
    When i move it to the left, observe what happens.
  • 00:02:37.090
    Now, when you run from here to here, the change in x is -4.0.
  • 00:02:45.100
    When you climb from here to here, the change in y is 3.0.
  • 00:02:51.200
    From this, the slope of this line is 3.0 divides by negative 4.0 which gives negative 0.75. Let me emphasize, the slope now is a negative number.
  • 00:03:02.050
    That is all for this lesson. You can move on to the practice questions to test your understanding.

Study Tips

This lesson is divided into 2 parts. The first part is to help you to familiarize with the terms 'change in x' and change in y'.
The second part is the actual lesson on the slope of a line.

When calculating the change, always 'run' first and then 'climb' up. The math video will illustrate more.

Know how to calculate the 'change in x' and 'change in y' before attempting to calculate the slope. This minimizes mistake.

Now, what is the definition for the slope of a line? It is defined as the ratio of the 'change in y' to the 'change in x'. This simply means that you just divide 'change in y' with 'change in x' to find the slope.

Watch the video to find out where these plane are located.
Visit the Q&A featuring categories such as Algebra, Graphs, Exponents and more. Also you can submit math question, share or give comments there.
Practice

Now , let's try some MCQ questions to understand this lesson better.
You can start by going through the series of the graphing linear equation question below

Question 1 on using a linear equation to calculate y-coordinates

Question 2 on the basics of graphing linear equations