Circumference and Area of A Circle

Click For Summary

Discussion Overview

The discussion revolves around methods for quickly calculating the circumference and area of a circle, exploring various approaches including ratios, series, and alternative mathematical techniques. Participants express interest in shortcuts and tactics for multiple-choice exams.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Some participants inquire about quick methods for finding the circumference and area of a circle, suggesting the use of ratios or series similar to the Pythagorean theorem.
  • One participant mentions that using the radius or diameter is the main way to find circumference and area, implying it is also the quickest method.
  • Another participant expresses a desire for a tactical approach to answering multiple-choice questions, comparing it to the Pythagorean concept.
  • One response suggests that learning the results is the only real shortcut and emphasizes using exact answers in terms of $$\pi$$ rather than approximations.
  • Several participants discuss using the approximation $$\pi \approx \frac{22}{7}$$ for calculations, with one mentioning the use of $$\frac{355}{113}$$ for more precision.
  • A participant shares a link to a resource on Vedic mathematics, asking for ideas on finding the nearest value of circumference and radius using this method.
  • Another participant provides rational approximations for calculating radius from area and circumference, using the approximation of $$\pi$$.

Areas of Agreement / Disagreement

Participants express various methods and approaches, but there is no consensus on a single best method for calculating circumference and area quickly. Multiple competing views and techniques remain present in the discussion.

Contextual Notes

Some methods discussed depend on approximations of $$\pi$$, and there are unresolved questions regarding the effectiveness of different shortcuts and their applicability in various contexts.

susanto3311
Messages
73
Reaction score
0
hello expert...

How to find the circumference of a circle and area of a circle quickly?
it's possible using method like ratio or series like pythagoras theory (3,4,5).
or another way?

somebody could help me out?

cheers...
susanto3311
 
Mathematics news on Phys.org
What do you know about the circle?
 
You can find both using the radius (or diameter) of the circle. The main way to find them is also the quickest way
 
hi guys...

i want to easy find area & circumference of circle to multiple choice exam with "tactics & logic" approach, again like triagle phytagoras concept just know 3,4 the last result must be 5..
 

Attachments

  • circle_problem.jpg
    circle_problem.jpg
    15.4 KB · Views: 118
I'm still not 100% sure what you're asking. I get the impression you want to know a way of finding the area of a circle without having to work it out in the same way that if you know two sides of a right angled triangle are 3 and 4 then the third must be 5.

If so then the only real shortcut is to learn the results. I would also use exact answers (left in terms of $$\pi$$) as it's both easier to work out and correct (not an approximation).

In multiple choice it may be worth saying $$\pi \approx 3$$



If you're given the diameter instead of the radius then you can use these formulae:

[math]C = \pi d[/math] and $$A = \frac{\pi}{4} d^2 $$ where $$d$$ is the diameter.

Just remember not to use that approximation too much...
[youtube]V98soOyQWKY[/youtube]
 
hello guys...

I found the nearest value of area of the circle with a simple trick using vedic maths..

please, read this link http://vedicmathstricks.yolasite.com/

how do make formula for find the nearest value of circumference of the circle?

any ideas?

thanks...
 
It appears to me what is being done there is to use 22/7 as an approximation for $\pi$ (I recall using this approximation in primary school). If you require more decimal places, then you can use 355/113.
 
susanto3311 said:
hello guys...

I found the nearest value of area of the circle with a simple trick using vedic maths..

please, read this link http://vedicmathstricks.yolasite.com/

how do make formula for find the nearest value of circumference of the circle?

any ideas?

thanks...

using vedic method, how to find easy radius? i mean simple calculation..
 
If we are given the area $A$ of a circle, or the circumference $C$, then using the rational approximation:

$$\pi\approx\frac{22}{7}$$

then we find:

$$A\approx\frac{22}{7}r^2\implies r\approx\sqrt{\frac{7A}{22}}$$

$$C\approx2\cdot\frac{22}{7}r\implies r\approx\frac{7C}{44}$$
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
Replies
1
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 24 ·
Replies
24
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K