Is 495.5 Equal to 495? A Mathematical Proof

  • Thread starter Thread starter zeromodz
  • Start date Start date
  • Tags Tags
    Proof
Click For Summary
The discussion centers around the mathematical assertion that 495.5 equals 495, which is challenged through various decimal representations. Participants argue about the validity of operations involving infinite decimals, particularly focusing on the equivalence of 0.999... to 1 and the implications for subtraction. There is confusion regarding the subtraction of 0.9 from both 100 and 99.999..., with some asserting that the results are incorrect. The conversation highlights the need for careful consideration of infinite decimal representations in mathematical proofs. Ultimately, the debate underscores the complexities and misunderstandings surrounding decimal notation and mathematical operations.
zeromodz
Messages
244
Reaction score
0
Sorry, I typed the wrong thing in the title, I meant 495.5 = 495

(1/3) + (1/3) + (1/3) = 1
(0.333333333333) + (0.33333333333) + (0.33333333333) = 1
0.999999999999999 = 1
99.9999999 = 100 (Multiplied by 10)
99.1 = 99 (Subtracted 0.9)
495.5= 495 (Multiplied by 5) <---------------PROOF
 
Mathematics news on Phys.org
Operations on infinite decimal representations need to be considered more carefully.
 
99.9999999 = 100 (Multiplied by 10)
99.1 = 99 (Subtracted 0.9)

This is not how subtraction is done

100-.9=99?

99.9999999... -.9=99.1?

Both wrong. Even if we assume that you flipped the equation so 100-.9=99.1, 99.99999-.9 is not 99
 
Office_Shredder said:
This is not how subtraction is done

100-.9=99?

99.9999999... -.9=99.1?

Both wrong. Even if we assume that you flipped the equation so 100-.9=99.1, 99.99999-.9 is not 99

The second one is right.
 
Werg22 said:
Office_Shredder said:
This is not how subtraction is done

100-.9=99?

99.9999999... -.9=99.1?

Both wrong. Even if we assume that you flipped the equation so 100-.9=99.1, 99.99999-.9 is not 99
The second one is right.

Umm... both 100-.9=99 and 99.999...-.9=99.1 are wrong. So I don't know what you're on about, plus it would've been a lot easier for the reader to determine which "second one" you're talking about by quoting just the relevant equality, not the entire post.
 
Mentallic said:
Umm... both 100-.9=99 and 99.999...-.9=99.1 are wrong. So I don't know what you're on about, plus it would've been a lot easier for the reader to determine which "second one" you're talking about by quoting just the relevant equality, not the entire post.

No, 99.9999...-0.9 = 99.0999... = 99.1 is correct.
 
Mentallic said:
Umm... both 100-.9=99 and 99.999...-.9=99.1 are wrong. So I don't know what you're on about, plus it would've been a lot easier for the reader to determine which "second one" you're talking about by quoting just the relevant equality, not the entire post.

There was nothing wrong with what Werg said. Yes (99.9999... - 0.9) really is equal to 99.1.

I can't believe this senseless OP is going to come back to yet another 0.9999... \neq 1 debate. :confused:
 
Oh yes of course, I didn't even stop to think about it once I saw all the recurring decimal places were cut off.
 

Similar threads

Seeking a reasonable mathematical explanation to a simple mathematical conundrum
  • · Replies 3 ·
Replies
3
Views
1K
I'm missing something re: proof by induction
  • · Replies 8 ·
Replies
8
Views
2K
Can the Infinite Sum of Natural Numbers Really Equal -1/12?
  • · Replies 6 ·
Replies
6
Views
3K
I found another easier way of solving y=x^k.
  • · Replies 5 ·
Replies
5
Views
2K
Playing with math keeps me sharp
  • · Replies 6 ·
Replies
6
Views
3K
Can Infinite Sums Be Manipulated by Shifting Terms?
  • · Replies 3 ·
Replies
3
Views
2K
Do Parentheses ALWAYS disappear after distribution?
  • · Replies 10 ·
Replies
10
Views
10K
MHB Algebraic Proofs and Verifying identities
  • · Replies 5 ·
Replies
5
Views
3K
Comp Sci Orbit of the Earth - numerical methods leapfrog
  • · Replies 3 ·
Replies
3
Views
2K
Commutative property of multiplication
  • · Replies 8 ·
Replies
8
Views
4K