B Is the volume of an exemplary cone equal to 4/3(pi)?

  • B
  • Thread starter Thread starter 5P@N
  • Start date Start date
AI Thread Summary
The discussion centers on the calculation of the volume of a cone, specifically questioning whether (4/27)*(3)^3 equals 4. Participants identify a critical arithmetic error in reducing (3)^3 to 9 instead of recognizing it as 27, leading to incorrect conclusions. The correct evaluation shows that (4/27)*27 simplifies to 4, confirming the volume calculation. Additionally, the importance of handling integer versus floating-point calculations in programming is highlighted, as it affects the outcome of the expression. Ultimately, the correct interpretation of the mathematical operations clarifies the confusion surrounding the volume of the cone.
5P@N
Messages
58
Reaction score
3
How is (4/27)*(3)^3 = 4?

When I evaluate it as a first step, I reduce the (3)^3 into 9, thus generating:

(4/27) * 9.

With a little basic multiplication, I have:
36/27, or 4/3.
Which is obviously not equal to 4!

Am I right or wrong? Where did I make an error?

Take a look if you please at the answer the author of this article has given as regards the volume of an exemplary cone at the beginning of his page. Did he, or did he not make an error in his final calculation? Or am I wrong? My conclusion is that the volume is 4/3(pi).
 
Mathematics news on Phys.org
3^3 is not equal to 9 (are you thinking of 3*3 ?)
 
Oh. Oops. my bad.
 
A small glitch: 3^3 = 27 not 9. Then answer is indeed 4
 
5P@N said:
How is (4/27)*(3)^3 = 4?

When I evaluate it as a first step, I reduce the (3)^3 into 9, thus generating:

(4/27) * 9.
Apart from the arithmetic error: This will be wrong if you enter the formula in a C program (or any programming language that handles integers separate from floating point numbers). Assuming 4 and 27 to be integers, 4/27 is 0 (it has to be a non-negative integer less than 1). And even if you do 3^3 as a floating-point calculation, you still have the 0 from the first division...

Thus: when dealing with integers, (4/27)⋅3^3 ≠ (4⋅3^3)/27!
 
5P@N said:
How is (4/27)*(3)^3 = 4?
5P@N , the multiply and divide operation are an equal priority operation with left associativity. The power is right associative operation and it's priority is higher than multiply and divide operations. Thus the expression can be written as:
4/27*3^3
and it is really equals 4
 
Last edited by a moderator:
##3^3## is not equal to ##9##

##3^3=3×3×3=27##

##\dfrac{4}{27}×27\;\;\implies\dfrac{4}{\not27}×\not{27}=4##

I hope it' ll help.
 
Back
Top