Is the answer in the second practice question wrong? My calculator said 9π is 28.27, not 28.26. Ps: if it is wrong I don't see a way to report it.

If you use π then you will get 28.27. If you use 3.14 then you will get 28.26.

hey i need help i don't understand can someone help me this is on my finals

and for area mutiply the radius by itself then multiply it by pie (3.14)

Who made pie because whoever did must of been really smart

No one really made it, Archimedes of Syracuse, was the first to calculate it.

yall why are the questions from 4 years ago-

The questions with the most votes are 4 years old, but if you go to the Sort by: and choose Recent, you will see questions that are 9, 10, and a month ago. Recent questions generally do not get many votes.

why do we need to measure circles

It is what other volumes are built off of and that can be useful for not over or under estimating liquid amounts and sends you to a higher GPA giving you a higher likely hood of going to your prefered collage

how to tell if your answer to circumference is correct

To find area with circumference, you divide the circumference by pi, to get your diameter. Then, you find the radius by dividing the diameter by 2. You then multiply your radius by itself and multiply that product by pi. Hope this Helps! :)

What should I do ,I need help

You should watch all of the videos again; they will help! If you are still having trouble, ask your teacher or your parent to help you!

Main content

Circumference review

CCSS.Math:

7.G.B.4

Google Classroom

Review the basics of circumference and try some practice problems.

What is circumference?

Circumference is the distance around the outside of a circle (its perimeter!).

Want a review of circle vocabulary terms (like pi, radius, and diameter)? Check out this video.

Finding circumference of a circle

To find the circumference of a circle, we can use either of the following formulas:

start text, C, i, r, c, u, m, f, e, r, e, n, c, e, end text, equals, pi, times, start text, d, i, a, m, e, t, e, r, end text

start text, C, i, r, c, u, m, f, e, r, e, n, c, e, end text, equals, 2, times, pi, times, start text, r, a, d, i, u, s, end text

Want to know why these formulas work? Check out this article.

Example 1: Finding circumference when given diameter

Find the circumference of a circle with a diameter of start color #1fab54, 3, end color #1fab54.

The formula for the circumference of a circle that uses diameter is:

C, equals, pi, start color #1fab54, d, end color #1fab54
C, equals, pi, start color #1fab54, 3, end color #1fab54
C, equals, start color #11accd, 3, pi, end color #11accd

We can stop here and write our answer as start color #11accd, 3, pi, end color #11accd. Or we can plug in 3, point, 14 for pi and multiply.

C, equals, 3, point, 14, dot, 3
C, equals, start color #11accd, 9, point, 42, end color #11accd units

The circumference of the circle is start color #11accd, 3, pi, end color #11accd units or start color #11accd, 9, point, 42, end color #11accd units.

Example 2: Finding circumference when given radius

Find the circumference of a circle with a radius of start color #7854ab, 8, end color #7854ab.

The formula for the circumference of a circle that uses radius is:

C, equals, 2, pi, start color #7854ab, r, end color #7854ab
C, equals, 2, pi, start color #7854ab, 8, end color #7854ab
C, equals, start color #11accd, 16, pi, end color #11accd

We can stop here and write our answer as start color #11accd, 16, pi, end color #11accd. Or we can plug in 3, point, 14 for pi and multiply.

C, equals, 3, point, 14, dot, 16
C, equals, start color #11accd, 50, point, 24, end color #11accd units

The circumference of the circle is start color #11accd, 16, pi, end color #11accd units or start color #11accd, 50, point, 24, end color #11accd units.

Practice

Problem 1

Suppose the radius of a circle is start color #7854ab, 5, end color #7854ab. What is its circumference?
Either enter an exact answer in terms of pi or use 3, point, 14 for pi and enter your answer as a decimal.

Want to try some more circumference of circle problems? Check out this exercise.

Sort by:

Want to join the conversation?

libwhac30
Posted 6 years ago. Direct link to libwhac30's post “how to tell if your answe...”
how to tell if your answer to circumference is correct
(0 votes)
Answer
- Aris13
  Posted 5 years ago. Direct link to Aris13's post “To find area with circumf...”
  To find area with circumference, you divide the circumference by pi, to get your diameter. Then, you find the radius by dividing the diameter by 2. You then multiply your radius by itself and multiply that product by pi.
  Hope this Helps! :)
  (14 votes)
Hanabi
Posted 4 years ago. Direct link to Hanabi's post “Is the answer in the seco...”
Is the answer in the second practice question wrong?
My calculator said 9π is 28.27, not 28.26.

Ps: if it is wrong I don't see a way to report it.
(7 votes)
Answer
- 106s.ewells
  Posted 4 years ago. Direct link to 106s.ewells's post “If you use π then you wil...”
  If you use π then you will get 28.27.
  If you use 3.14 then you will get 28.26.
  (11 votes)
Kamran Pallier
Posted 6 years ago. Direct link to Kamran Pallier's post “It all depends on how you...”
It all depends on how you view easy as. If you haven't learnt circumference for a while or are new to the subject, some people can find it challenging.
(2 votes)
Answer
- Hannabli
  Posted 6 years ago. Direct link to Hannabli's post “Actually, you're supposed...”
  Actually, you're supposed to have learned about these basic circle terms in around 4th or 5th grade... depends on what you're doing with the circles though....
  (1 vote)
Jalon
Posted 4 years ago. Direct link to Jalon's post “hey i need help i don't u...”
hey i need help i don't understand can someone help me this is on my finals
(7 votes)
Answer
- mkdhensa
  Posted 2 years ago. Direct link to mkdhensa's post “and for area mutiply the ...”
  and for area mutiply the radius by itself then multiply it by pie (3.14)
  (4 votes)
Kenny Rhine
Posted 2 years ago. Direct link to Kenny Rhine's post “Who made pie because whoe...”
Who made pie because whoever did must of been really smart
(5 votes)
Answer
- KC
  Posted 2 years ago. Direct link to KC's post “No one really made it, Ar...”
  No one really made it, Archimedes of Syracuse, was the first to calculate it.
  (7 votes)
venus
Posted 2 years ago. Direct link to venus's post “yall why are the question...”
yall why are the questions from 4 years ago-
(5 votes)
Answer
- David Severin
  Posted 2 years ago. Direct link to David Severin's post “The questions with the mo...”
  The questions with the most votes are 4 years old, but if you go to the Sort by: and choose Recent, you will see questions that are 9, 10, and a month ago. Recent questions generally do not get many votes.
  (7 votes)
20.cordovaeduardo
Posted 4 years ago. Direct link to 20.cordovaeduardo's post “why era there so much kha...”
why era there so much khan academy assinments
(6 votes)
Answer
- ferminmundo
  Posted 10 months ago. Direct link to ferminmundo's post “im sorry it was my fault”
  im sorry it was my fault
  (1 vote)
Jayden
Posted 2 years ago. Direct link to Jayden's post “Hello, since the weather ...”
Hello, since the weather is terrible today, and my wifi is oging in and out, can someone explain this to me thanks!
(5 votes)
Answer
- ferminmundo
  Posted 10 months ago. Direct link to ferminmundo's post “no excuses hehehehe”
  no excuses hehehehe
  (2 votes)
chloe.engle
Posted 6 years ago. Direct link to chloe.engle's post “What should I do ,I need ...”
What should I do ,I need help
(0 votes)
Answer
- 🅰🅽🅶🅴🅻 🆉🅷🅾🆄
  Posted 2 years ago. Direct link to 🅰🅽🅶🅴🅻 🆉🅷🅾🆄's post “You should watch all of t...”
  You should watch all of the videos again; they will help!
  
  If you are still having trouble, ask your teacher or your parent to help you!
  (2 votes)
garciadavid
Posted 5 years ago. Direct link to garciadavid's post “why do we need to measure...”
why do we need to measure circles
(2 votes)
Answer
- Patton_Shawn Livingston
  Posted 3 years ago. Direct link to Patton_Shawn Livingston's post “It is what other volumes ...”
  It is what other volumes are built off of and that can be useful for not over or under estimating liquid amounts and sends you to a higher GPA giving you a higher likely hood of going to your prefered collage
  (2 votes)

7th grade

Unit 6: Lesson 1