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

Using inequalities to solve problems | Solving equations & inequalities | Algebra I | Khan Academy


2m read
·Nov 10, 2024

We're told that Kayla wants to visit a friend who lives eight kilometers away. She'll ride the subway as far as she can before walking the rest of the way. First, she needs to buy an access pass that costs five dollars and fifty cents. There is also a fee of 1.25 per stop. This is an expensive subway. Kayla doesn't want to spend more than 15 on the trip, so she wants to know the largest number of stops she can afford.

Let s represent the number of stops that Kayla buys. So first, pause this video and see if you can write an inequality that describes how many stops or that describes the situation that describes that she wants to take as many stops as she can, but she doesn't want to spend more than 15 dollars.

All right, now let's do this together. So first, let's just think about an expression for how much she spends. No matter what, she's going to spend five dollars and fifty cents. So we could write it like this: So five dollars and fifty cents, that's what she's going to spend even if she doesn't take any stops, and it's 1.25 per stop.

And s is the number of stops, so the amount she's going to spend just from the stops is going to be 1.25 times s. So it's going to be plus 1.25 s. This is the upfront she has to spend, and this is how much she's going to spend on stops. And this is an s right over here, and I wrote a 5 right next to it. They look kind of similar.

And we know that she doesn't want to spend more than 15, so she's willing to spend up to 15. So this total amount that she spends has to be less than or equal to 15 dollars, or if we didn't write it with the dollar symbols, we would write 5.50 plus 1.25 s is going to be less than or equal to or needs to be less than or equal to 15.

Now that we've written this inequality, what is the number of stops that Kayla can afford? What's the largest number of stops that she can afford? Pause this video and try to figure that out.

Well, to figure that out, we just have to solve for s and then figure out what the largest s is that satisfies the inequality once we've solved for s. So the first thing I would do is subtract 550 from both sides. When we do that, we are left with 1.25 s is less than or equal to 9.50.

Then I would divide both sides by 1.25, and since I'm dividing both sides by a positive value, it doesn't change the direction of the inequality. 9.50 divided by 1.25 is equal to 7.6. So we get that s needs to be less than or equal to 7.6.

So we can't take a fractional number of stops. The largest number of stops that Kayla can take is going to be seven stops. She can't take eight, and she can't take seven and a half or seven point six, so the largest number she can take is seven stops. So she can take as many as seven stops, and we are done.

More Articles

View All
A private jet for $500,000?
Steve: “I’ve heard about these jets called Haers. Yeah, what about them? I didn’t even know they exist. Could you tell me a little bit more about them?” Sure, of course! Come over here. These are the airplanes. They’re really inexpensive from the standpo…
Terry Crews Skydives Over Iceland | Running Wild with Bear Grylls
Like a dream. Let’s get your chute up. I’m ready. Here we go. BEAR GRYLLS: Terry Crews and I just landed on a small airfield in the Icelandic mountains. Last night, he told me that skydiving was on his bucket list. Well, Terry, be careful what you wish f…
The Middle Class Just Got FINANCIALLY RUINED
What’s up, Graham? It’s guys here. So how should I say this gently? Uh, we’re screwed. It was just reported that household debt reached an all-time high of 16 trillion dollars. Credit card debt is on the rise. One in three Americans making 250,000 is livi…
Kevin O'Leary on What it Takes to Get Rich
[Applause] Tell you what, I’d like to do tonight. I thought I’m going to have some fun. You know, people always ask me, “Why do I do television? What does that have to do with being an investor? Is there any synchronicity between the hobby of TV?” Really…
My Response To Dave Ramsey
What’s up you guys? It’s Grahe here. So I normally don’t make response videos here in the channel, but after watching a 1-hour upload from the personal finance host Dave Ramsey, I wanted to dive deeper into one of the most controversial and debated topics…
Electromagnetic Levitation Quadcopter
How much does this thing weigh? -Well, try to pick it up. -Okay. Alright. -Be nice to it. -105 lbs -105 lbs -It consists of four motors connected up to these spinning magnet arrays, and if you spin these fast enough, it will actually levitate. -That’s cor…