yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Writing y = mx proportional equations worked example 1 | Grade 8 (TX) | Khan Academy


2m read
·Nov 10, 2024

We are told in a rowing exercise Claudia completes 450 strokes in 15 minutes. Write an equation that can be used to find the number of strokes y she can row in x minutes. So, pause this video and see if you can figure that out.

All right, now let's think about this together. So what I'm actually going to do is a little bit of a table here, and I'm going to put the number or I'll put time here in minutes, and this is going to be our x variable. And then over here, I'm going to put strokes, and this is going to be our y variable.

So they've already told us one that after 15 minutes—and everything here is in minutes—that Claudia was able to do 450 strokes. Is there maybe another point we can think about? Well, let's think about what happens at zero minutes. How many strokes would Claudia have done? Well, she wouldn't have done any at that point. She hadn't had a chance to do any strokes.

And so now there's something interesting going on here. We can see that when time is increasing by 15, how much are the strokes increasing by? Well, they're increasing by 450. Or another way to think about it is what is our change in y over change in x, or a change in strokes per change in time? Well, we can calculate that now. That's going to be 450 strokes for every 15 minutes.

And this we can see: 450 divided by 15 is going to be 30. And we can even write the units down—this is in strokes per minute.

Now, you might also recognize that this is the same definition as what we normally consider to be slope. So how can I write this as an equation? Well, my y, the number of strokes, is just going to be this unit rate—how many strokes per minute—which is also going to be my slope. It's just going to be that which we could consider m times x.

And you could try it out for these two points: when x is zero, y is zero; when x is 15 minutes, y is 450 strokes. And we are done.

More Articles

View All
EVERYTHING WRONG With My Tesla Model 3 After One Year
What’s up you guys? It’s Graham here. So, as some of you know, last year I bought a Tesla Model 3. In typical me fashion, I tried to be as frugal as possible to get the car’s price down as much as I could by skimping on all of the options. I decided to p…
Blacksmith for Barter | Live Free or Die
Gonna be a hot one today in the mountains of Colorado. Primitive blacksmith Derik fires up his forge to nearly 2500 degrees, the ideal temperature to mold iron. Today I’m gonna continue working on my camp set, try to finish that out—four more pieces beca…
Tax, discount and tip examples
We’re told that Casey buys a bracelet. She pays for the bracelet and pays 72 cents in sales tax. The sales tax rate is 6%. What is the original price of the bracelet before tax? So pause this video and see if you can figure this out. Well, let’s think a…
Interview: Donald Trump with Rona Barrett - October 6, 1980
Got this telegram from Rona Barett, and it said, “Would you stop fussing around after seven and a half years?” What do you think she meant by fussing? That’s very funny. And Elton said, “Leonard, obviously she couldn’t tell you what she really meant becau…
7 Lessons For Creatives From Nikola Tesla
Nikola Tesla was an inventor, electrical engineer, and physicist. He’s seen as one of the greatest engineers and inventors of all time and is best known for his contributions to the modern electricity supply system. Tesla spent a great portion of his life…
Putting a Species on the Map | Explorers Fest
[Applause] Thank you. Last time I was here in DC, I had the chance to be on stage. You know what I did? I came flying just like that. Many people have been asking me, do you still fly? The answer is yes, I fly every day, and I enjoy it. And the hope today…