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Course: 6th grade foundations (Eureka Math/EngageNY)>Unit 5

Lesson 1: Topic A: Foundations

Area & perimeter word problem: dog pen

Sal figures out the width of a dog pen. Created by Sal Khan.

Want to join the conversation?

• How would you figure the area of a pentagon?
• I do not know
• Lisa built a rectangular flower garden that is 4 feet wide and has a perimeter of 26 feet.
• First, you multiply the width by 2. The product is 8. Next, you subtract 8 from the perimeter which is 26, and the difference is 18. Afterwards, 18/2 = 9. This means that 9 is the length. If you want to figure out the area, just multiply 4 and 9, and the product is 36 feet squared.
• How to calculate depth?
• Depth is not something that you would calculate so much as you would just measure it. You would need a starting place - something like sea level (the surface of the sea), then you would just measure down to the bottom to find depth.
• Is there another way of doing this?
For example, what I learned was 78/2 and then take that answer and subtract by the one length that the problem gives you, because the formula that I learned was 2(L+W).

And also, which is the fastest and easiest way of doing this??
• there is definitely many ways to solve the problem. the way you mentioned is one of them.
• *What if they don't give you the length? And they just give you the area and height?*
• do the same thing but with the height in the place of the length
• im stuc

The area of a square is 144 square centimeters.
What is the length of one side of the square?
• The area of a square is the side length times itself. So we need to find what positive number times itself would give 144. This positive number is 12. (This process is called taking the square root.)

The area is given in square centimeters, so the side length is in centimeters.

So the side length is 12 centimeters.
• how do you find the area of a cricle
• The formula is pi times the radius squared.
I hope this helped a bit!
Edit: Ask me if you need help :)
• At Arcane.
Well for starters, I keep getting the formulas mixed up, word problems are not my strong suit, I know they different things, but they sound the same. I'm doing my best, but I'm not good with words, so I'll try to give you my best example.
The question up in the video, I don't even know where to begin with that one! I don't know how to get started, I can finish it. What's area and priemeter?? And how to know when to multiply and add. I already know how to do those. I'm not sure if that made any sense.(Sweat)I'm not complaining, I'm sorta desperate, although I'm just passing by. However, if anyone can like give me a tip! I'll be grateful, you just helped out a person in need. (Me Blushing Sheepish)I'm willing to learn. Please.

June 27th, 2021.
• The perimeter is the total distance around the edges of a shape. So we add the edges to find the perimeter. This means that the perimeter of a rectangle is twice the length plus twice the width.

The area is the amount of space (or number of unit squares) inside the shape. So if the figure is a rectangle, we can multiply length times width to find the area.

Have a blessed, wonderful day!
• So what would the square unit area be if you have a primeter of 56 if thats all they give me?
• i did it. it took me 2 1/2 hours

Video transcript

Mike built a rectangular dog pen that is 21 feet long and has a perimeter of 78 feet. What is the width of Mike's dog pen? So let's draw what it might look like. So it might look something like this. I'll do my best to draw it, a rectangle or potential dog pen. So let's say that this is the dog pen right over here. And they give us its length. Its length is 21 feet. So this distance right over here is 21 feet. And of course, if that distance is 21 feet, this distance is also going to be 21 feet. Now, they also tell us that the perimeter is 78 feet. So the perimeter is 78 feet. So we need to figure out the width. And the width would be this length-- or this width, I should say-- this width, which is going to be the same thing as that width right over here. So let's think about. And we know how we figure out the perimeter. If we added this distance, 21 feet, to this distance, the width, plus 21 feet to the width again, we're going to get to 78 feet. So one way to back into what the width is is to say, well, look if we sum up all of these lengths, we're going to get 28 feet. So let's at least subtract these two orange lengths, the two 21 feet, from the 78 feet. And then we figure out how much length essentially these two widths have to make up. So let's subtract. Let's do 78 minus 21 minus 21. And what's that going to be equal to? So that's 78 minus 42. And 78 minus 42-- I don't want to make a careless mistake-- 78 minus 42 is going to get me to 36. So this is equal to 36. And let's remind ourselves what 36 feet is. That's the total length-- or I should say the total width-- if we were to take the width down here and add it to the width up here. Now, we know something else. These are the exact same width, that this distance is the same as this distance. And if we add them together, we get to 36. So what are two distances, or what are two numbers that I can add together to get to 36? Well, we know that 18 plus 18 is equal to 36. So this one down here must be 18. And this one up here must also be 18. And we can verify that. Try adding all of these up together. You add the two widths. You get 18 plus 18. And you add the two lengths, plus 21 plus 21. And you are left with 36, which is exactly what we got here. This is what we needed the two widths to add up to-- plus 42. Which is, of course, equal to-- 36 plus 42 is equal to 78, which is the perimeter.