Assuming something is equal to 1

  • Context: High School 
  • Thread starter Thread starter gladius999
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the practice of assuming certain constants or variables equal to 1 in mathematical equations, particularly in the context of physics and problem-solving. Participants explore the conditions under which such assumptions are valid and the implications for the equations involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that assuming a value is equal to 1 can simplify equations, particularly when the value is arbitrary and does not affect the generality of the solution.
  • One participant provides a specific example involving a system of equations and discusses the implications of assuming a variable equals 1, breaking it down into cases based on whether the variable is zero or non-zero.
  • Another participant questions the validity of dividing by zero in the context of these assumptions, indicating a need for clarification on the mathematical operations involved.
  • A gas law example is introduced, where participants discuss the constants involved and whether they can be assumed to be equal to 1 under certain conditions.
  • One participant emphasizes that while it is not generally valid to assume something equals 1, it can be acceptable in specific contexts, such as when defining units in physics.

Areas of Agreement / Disagreement

Participants express differing views on the general validity of assuming values equal to 1, with some arguing for its utility in specific contexts while others caution against overgeneralization. The discussion remains unresolved regarding the broader implications and conditions for making such assumptions.

Contextual Notes

Participants highlight limitations in understanding when assumptions can be made, particularly regarding the treatment of zero and non-zero values in equations. There is also a dependence on the definitions of constants and the context of the problems being discussed.

gladius999
Messages
60
Reaction score
0
I have always seen people solving equations while assuming something is equal to 1 (usually a constant). Why and under what circumstances can you assume this? what equations are still valid after u assume that it is 1?

Thanks
 
Mathematics news on Phys.org
Post an example, and we can explain why it's a good assumption. Usually you assume a value is equal to 1 because it could be anything (not that you don't know what it is, but that it's arbitrary) and then by assuming it's 1, you can prove that it doesn't satisfy a property for any arbitrary value
 
a+2b+c=d
2a-b-4c=d
a-c=d

u can assume d=1?
 
Ok, good example. You actually have to break this up into two cases:
1) d=0. If d=0, you can just solve the equation since there are three equations and three unknowns.

2) d =/= 0. If d is non-zero, divide both sides of every equation by d. Call A=a/d, B=b/d, C=c/d. Then we get A+2B+C=1, 2A-B-4C=1, A-C=1 Then every solution of (A,B,C) corresponds to a set of solutions (Ad,Bd,Cd,d) where d is arbitrary. So we can essentially assume that d=0 or d=1 since we can derive all the solutions from this
 
Last edited:
hmm i seem to understand number 1)
but 2) i don't get how u can divide both sides of every equation by zero.

another gas example:
P1V=n1RT1
P2V=n1RT2

where V and R are constants

when solving equations can u assume V and R is 1?
 
Well R is a constant. It's the gas constant but if in the specific situation you're looking at the volume doesn't change then you can say n1RT1/P1=V and n2RT2/P2=V therefore you can say n1RT1/P1=n2RT2/P2. as for Office Shredder's post when he said "If d is non-zero, divide both sides of every equation by zero" he actually meant "If d is non-zero, divide both sides of every equation by d". I suspect he just had a brain fart and the fingers typed something different then he was thinking.
 
Yeah, that was just a mistype. I fixed my post to reflect what you should actually do
 
thnx for ur quick reply guys, i will try apply ur ideas into my thinking:)
 
You cannot, in general, "assume something is equal to 1". But if you are talking about measured quantitities in physics, you often can assume a system of units so that value is 1 of whatever units you are using. For example, in the standard "meter-seconds" system, the speed of light is 299,792,458 meters per second. But can, just as well take "the distance time travels in one second", one "light second", to be my distance unit rather than the meter. In that case, the speed of light is 1 "light second per second".
 

Similar threads

  • · Replies 13 ·
Replies
13
Views
2K
High School Potato paradox
  • · Replies 28 ·
Replies
28
Views
3K
  • · Replies 22 ·
Replies
22
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 22 ·
Replies
22
Views
3K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 25 ·
Replies
25
Views
3K