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
4 Reasons to Invest NOW | Ask Mr Wonderful Shark Tank's Kevin O'Leary
Sometimes the entire year’s return comes in just a few days, and if you’re not invested in those days, you miss out. Your 20s and 30s are prime earning years. The longer you wait, the less you will have in retirement, so it’s best you get started right no…
The History of Magic | StarTalk
What’s this with Escape artists? I never was as enchanted by that as others have been. When you’re talking about a escape artist, you’re really talking about Houdini and then a lot of knockoffs after that. Houdini, in the early 20th century, a man born in…
Tidepooling along the Pacific Coast | National Geographic
Nature, the most powerful creative force on Earth. I’m Chef Melissa King. Cooking has taken me to incredible places. Magical. (laughs) From TV competitions and celebrity galas to countries around the world, I’m heading out to places I’ve never been before…
The Big Risks Of Alibaba Stock (Delisting, Accounting, VIE, Anti-Monopoly)
Well, I said the next video I was going to be talking about the super investors, but you guys were very keen to discuss the risks behind Alibaba stock. So, I thought I’d better make this video first. In the last video, we did a deep dive on how Alibaba’s…
I Didn't know Birds use Math in Murmurations! - Smarter Every Day 234
I don’t know why, but every day in that tree right there, birds congregate together. Then, at some point, they lift off and they start flying together in a flock. You got all these birds that are just moving almost like they’re a macro-organism. You’ve go…
Safari Live - Day 269 | National Geographic
This program features live coverage of an African safari and may include animal kills and carcasses. Viewer discretion is advised. Hello, hello and good afternoon and welcome to the sunset Safari where I’ve got some very exciting news and I will tell you…