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

Finding missing side when given area | Math | 3rd grade | Khan Academy


2m read
·Nov 11, 2024

The picture has an area of 80 square cm. What is the width of the picture?

So here's our picture: this super fun giraffe listening to music. Our picture's shape is a rectangle, and we're asked to find the width of that rectangle.

Well, maybe we don't know a special formula or a special equation to find the width, but we do know one to find the area of a rectangle. So let's use that formula and see how it can help us.

We know that the area of a rectangle can be found by multiplying the length of the rectangle over here—the length times the width. So if we multiply the two side lengths of a rectangle, we get its area.

In this picture, and this rectangle, we are told that our area is 80 square cm. So we already know the area, and we can use that to help us. We also know the length; we're told that this distance from here to here, this length, is 10 cm.

So the length is 10 times the width. We don't know the width, that's what we're looking for. What we do know, though, is that we need our width to be a number that when it's multiplied by 10, we get 80 for an answer.

So what number times 10 equals 80? It's 8. 8 times 10 equals 80. So that means the width of our picture is 8 cm.

Let's try one more: a rectangle has an area of 24 square m. The width of the rectangle is 4 m. What is the length of the rectangle?

So this time we don't even have a picture to look at, but we have enough information up here to solve this. Again, we can use our formula that tells us the area of a rectangle is the length times the width.

Now, we could draw this rectangle, it might be helpful to visualize it, but I'm going to show you here we could actually solve it without ever even seeing the rectangle because we know the area is 24 square m.

So the space the rectangle covers is 24 square m, and the length—we don't know the length; we're asked what is the length—but we do know that the width is 4 m.

So our length has to be some number that when it's multiplied times 4, we get 24 for the answer. That number must be 6, because 6 times 4 equals 24.

So the length of our rectangle is 6, and in this case, we're talking about meters.

More Articles

View All
5 Habits Of The Sigma Male
I’m sure that you have heard of the alpha and beta males at some point in your life. In popular culture, these terms, based on the alphabet, are used to describe male personality types. An alpha male can be considered the man at the top of the dominance h…
Canceling zeros when dividing | Math | 4th grade | Khan Academy
Let’s solve 350 divided by 50. So one way to think about this is if we had 350 of something, let’s say something delicious like brownies. If we had 350 brownies and we were dividing them into groups of 50, how many groups of 50 could we get? Well, one ide…
Diego Saez Gil - How Pachama Uses Tech to Solve Climate Change
Alright guys, welcome to the podcast! How’s it going to you? It’s going great. So today we have Diego Sayis Gil of Pochamma from the Winter ‘19 batch and Gustav Helstrom, who is a partner at YC. So today we’re here to talk about Diego’s company. Gustav, w…
The greenhouse effect | Physics | Khan Academy
Our Earth’s surface temperature is somewhere close to 15° C—nice, cozy, and warm for us living beings. But what keeps us so warm? Well, my instinctive answer is that it’s the sun, right? But it actually gets more interesting. Our atmosphere has these gase…
Mars Gets Ready for Its Close-up | Podcast | Overheard at National Geographic
I’m getting to go on a guided tour of Mars. This is so freaking cool! You can see this spectacular panoramic landscape. This could be Canyonlands; this could be Death Valley. What’s the weather like in this section of Mars? Yeah, the forecast for tomorro…
Running Your Company by Patrick Collison
So Patrick welcome. So Patrick is the co-founder and CEO of Stripe. He launched the startup, we’re now a pretty big company in 2010, correct? With his brother John. Why should we started working on it full-time in 2010? But it actually your comment just t…