Video

Writing proportional equations (1) (Full video)

Khan Academy

Supporting grades: 7

Description: Sal figures out the constant of proportionality when dealing with a constant rate. Write an equation that shows the relationship between the distance he runs, d, in kilometers and the time he spends running, h, in hours. One way is to say, look, he's running at a constant rate, so his distance is going to be equal to some constant, let's just call that lowercase k, times the amount of time he spends running, and the way that we can figure out what k is is by using the information that they gave us. All right, well there's a bunch of ways to solve for k, but one way is to say, let's just divide both sides by two hours.

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