how to perimeter of a semiircle on top of a triangle?

annie, to find the perimeter of a semicircle on top of a triangle, you have to know 3 things: 1) The word "*semicircle*" literally means "*half of a circle*". 2) The formula for calculating the perimeter of a circle (Which is `pi*d`, where *d* is going to be the diameter of the circle --- or in our case the semicircle, and *pi* means the number π -- or 3.141592653.....) 3) You need to realize that because the semicircle is on top of the triangle, the length of that side of the triangle is going to be the same as the diameter of the semicircle. Now, because of fact #1 above, all you need to do is calculate the perimeter of a circle (using facts #2 and #3) and then divide the answer by 2. In other words `Perimeter of semicircle = (pi*d) ÷ 2` If you now want to calculate the perimeter of the semicircle _*and*_ the triangle together, then all you have left to do is to add the length of the other two sides of the triangle to the perimeter of the semicircle. I hope this information helps you to understand so that you will be able to do similar problems in the future. :)

What if its a paralellogram? how would i find the area?

How you can find the area is length times width.

So for an octagon or hexagon we would just multiply by the number of the sides and the length of each side?

Its not always like that. You could only do that when all your sides lengths are equal. Say you have a octagon with equal length of sides = 5 , then you could find the perimeter by multiplying the number of sides by the length. In this case, 8 x 5 = 40. But if all your sides are not equal then you have to add them one by one.

at 1:20 how does the square equal 28?

Well, the question was asking for the _perimeter_ of the square. A square's sides are all congruent. A formula for perimeter for _* squares*_ is 4 _s_ (with _s_ being the side length). The problem states that one side is equal to 7 m. So in the equation, replace s with 7. So the equation is now 4(7) = P (P is perimeter) 4 times 7 = 28 m, and that's how they got 28 m.

why is it called a perimeter?

“Peri-“ means “around”, and “meter” refers to measurement. That makes sense because the perimeter is the *measure around* a shape. I hope this helps!

It's sort of long to count squares - Is there a straightforward way?

Whenever you see a compound shape (one with multiple shapes attached to it), then you should multiply the length by the width. Looking at the example in the video [0:00 - 0:58], the compound shape can be broken up into 3 shapes: 1) 2 by 5 rectangle (4 + 2 + 5 + 1 = 12) 2) 1 by 2 rectangle (2 + 2 + 1 = 5) 3) 1 by 3 rectangle (3 + 3 + 1= 7) Then add all of those up and you should get the 24 squares, the same answer that you would have gotten if you were to count all of them the long way.

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3rd grade

Course: 3rd grade > Unit 11

Lesson 1: Perimeter

Perimeter of a shape

Name: Perimeter of a shape
Uploaded: 2013-08-02T22:23:27Z
Description: To find the perimeter of a shape, you add up the lengths of all the sides. For a square or pentagon, it's even easier - you can multiply the length of one side by the number of sides to get the total perimeter.

Google Classroom

To find the perimeter of a shape, you add up the lengths of all the sides. For a square or pentagon, it's even easier - you can multiply the length of one side by the number of sides to get the total perimeter. Created by Sal Khan.

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annie stokes
Posted 10 years ago. Direct link to annie stokes's post “how to perimeter of a sem...”
how to perimeter of a semiircle on top of a triangle?
Button navigates to signup pageComment on annie stokes's post “how to perimeter of a sem...”
(58 votes)
Answer
- Project
  Posted 10 years ago. Direct link to Project's post “annie, to find the perime...”
  annie, to find the perimeter of a semicircle on top of a triangle, you have to know 3 things:
  1) The word "semicircle" literally means "half of a circle".
  2) The formula for calculating the perimeter of a circle (Which is pi*d, where d is going to be the diameter of the circle --- or in our case the semicircle, and pi means the number π -- or 3.141592653.....)
  3) You need to realize that because the semicircle is on top of the triangle, the length of that side of the triangle is going to be the same as the diameter of the semicircle.
  Now, because of fact #1 above, all you need to do is calculate the perimeter of a circle (using facts #2 and #3) and then divide the answer by 2. In other words Perimeter of semicircle = (pi*d) ÷ 2
  If you now want to calculate the perimeter of the semicircle and the triangle together, then all you have left to do is to add the length of the other two sides of the triangle to the perimeter of the semicircle.
  
  I hope this information helps you to understand so that you will be able to do similar problems in the future. :)
  Comment on Project's post “annie, to find the perime...”
  (22 votes)
Shahin Ramezani
Posted 7 years ago. Direct link to Shahin Ramezani's post “but what if the perimeter...”
but what if the perimeter and area are the same
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(15 votes)
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Void_Ent1ty
Posted 4 years ago. Direct link to Void_Ent1ty's post “Where does the word Perim...”
Where does the word Perimeter come from?
Button navigates to signup pageComment on Void_Ent1ty's post “Where does the word Perim...”
(13 votes)
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szhao
Posted 9 years ago. Direct link to szhao's post “So for an octagon or hexa...”
So for an octagon or hexagon we would just multiply by the number of the sides and the length of each side?
Button navigates to signup pageButton navigates to signup page
(4 votes)
Answer
- Rohini
  Posted 9 years ago. Direct link to Rohini's post “Its not always like that....”
  Its not always like that. You could only do that when all your sides lengths are equal. Say you have a octagon with equal length of sides = 5 , then you could find the perimeter by multiplying the number of sides by the length. In this case, 8 x 5 = 40. But if all your sides are not equal then you have to add them one by one.
  Comment on Rohini's post “Its not always like that....”
  (7 votes)
billybrookes5
Posted 9 years ago. Direct link to billybrookes5's post “at 1:20 how does the squa...”
at
1:20
how does the square equal 28?
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(4 votes)
Answer
- Rossa
  Posted 9 years ago. Direct link to Rossa's post “Well, the question was as...”
  Well, the question was asking for the perimeter of the square.
  A square's sides are all congruent.
  A formula for perimeter for * squares* is 4 s_ (with _s being the side length).
  The problem states that one side is equal to 7 m. So in the equation, replace s with 7.
  So the equation is now 4(7) = P (P is perimeter)
  4 times 7 = 28 m, and that's how they got 28 m.
  Comment on Rossa's post “Well, the question was as...”
  (6 votes)
240480
Posted 3 years ago. Direct link to 240480's post “why is it called a perime...”
why is it called a perimeter?
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(4 votes)
Answer
- Johanna
  Posted 3 years ago. Direct link to Johanna's post ““Peri-“ means “around”, a...”
  “Peri-“ means “around”, and “meter” refers to measurement. That makes sense because the perimeter is the measure around a shape.
  
  I hope this helps!
  Button navigates to signup page
  (6 votes)
ThomasH
Posted 7 months ago. Direct link to ThomasH's post “I don't have a question.w...”
I don't have a question.what
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(6 votes)
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LANDON267
Posted 4 years ago. Direct link to LANDON267's post “What if its a paralellogr...”
What if its a paralellogram? how would i find the area?
Button navigates to signup pageComment on LANDON267's post “What if its a paralellogr...”
(5 votes)
Answer
- 28ed27356
  Posted a year ago. Direct link to 28ed27356's post “How you can find the area...”
  How you can find the area is length times width.
  Button navigates to signup page
  (2 votes)
Angelina Snow
Posted 5 years ago. Direct link to Angelina Snow's post “It's sort of long to coun...”
It's sort of long to count squares - Is there a straightforward way?
Button navigates to signup pageButton navigates to signup page
(3 votes)
Answer
- Lanz Sidney Povey
  Posted 5 years ago. Direct link to Lanz Sidney Povey's post “Whenever you see a compou...”
  Whenever you see a compound shape (one with multiple shapes attached to it), then you should multiply the length by the width.
  
  Looking at the example in the video [
  0:00
  -
  0:58
  ], the compound shape can be broken up into 3 shapes:
  1) 2 by 5 rectangle (4 + 2 + 5 + 1 = 12)
  2) 1 by 2 rectangle (2 + 2 + 1 = 5)
  3) 1 by 3 rectangle (3 + 3 + 1= 7)
  
  Then add all of those up and you should get the 24 squares, the same answer that you would have gotten if you were to count all of them the long way.
  Comment on Lanz Sidney Povey's post “Whenever you see a compou...”
  (5 votes)
Sofia
Posted 3 years ago. Direct link to Sofia's post “Where does the word Perim...”
Where does the word Perimeter come from?
Button navigates to signup pageButton navigates to signup page
(4 votes)
Answer
- wryee2nd
  Posted 9 months ago. Direct link to wryee2nd's post “same question”
  same question
  Button navigates to signup page
  (1 vote)

Video transcript

What is the perimeter of the shape? Each square in the grid is a 1 by 1 centimeter square. So all we have to do is add up the lengths of these blue segments right over here. And they put it on this nice grid. And each box here is 1 by 1. So let's say we start up here. We want to make sure that we only go to where we started and we don't double count. So this perimeter is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 centimeters long. So it is 24 centimeters. The other way we could have thought about this is you could have looked at the length of each of these sides. So this is 1 plus 2 plus 3 plus 1 plus 3 plus 1 plus-- what is this-- 5 plus 2 plus 4 plus 2. And you would have also gotten 24 centimeters. Let's do a couple more of these. What is the perimeter of the square? So once again, it's the length of all of the segments that define the outside boundary of the square. And by definition, a square-- all of its sides are equal. So you have 4 sides that are all 7 meters long. So you could say it's 7 meters plus 7 meters plus 7 meters plus 7 meters, or it's 4 times 7 meters or 28 meters. Let's do one more. What is the perimeter of the regular pentagon? So it's a regular pentagon, which means all of its sides have the same length. And they give us a side of one. The length of one is 2. So all of the sides have length 2. So it's going to be 2 plus 2 plus 2 plus 2 plus 2, or essentially five 2's. Or another way of thinking about it is it's 5 times 2, which is going to be 10. You have five sides of this pentagon. Each of those sides are 2 units long. So 2 units long times 5 sides is going to be 10 units.