Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I have two equations:

(1) $\displaystyle y = \frac {0.0060}{k}$

(2) $\displaystyle y= \frac{0.00016}{m}$

In the first equation, $k$ is held constant and in the second equation, $m$ is held constant.

How do I determine which variable has a greater affect on $y$?

E.g., how do I determine if doubling $k$ as a greater effect on $y$ than doubling $m$ and so forth?


share|improve this question
If k and m are held constant, then y in each equation does not change. –  Ross Millikan May 21 '11 at 20:16

1 Answer 1

Dear user, both relationships are called "inverse proportionality", so they have exactly the same effect: doubling of $k$ in the first case as well as doubling of $m$ in the second case reduces $y$ to one-half of its value.

share|improve this answer
Thanks @Lubos, so there is no other way in which you would comment on how m and k affect y differently? –  user10265 May 21 '11 at 12:17
@user10265: As was pointed out above, if $m$ is doubled, the relative change is the same as when $k$ is doubled. The absolute changes are different, but in most physical situations it is relative change that matters. To calculate absolute change, find the difference between $y$ at $m$ and $y$ at $2m$, and do the same for $k$ and $2k$. Which absolute change is bigger and which is less will depend on the values of $m$ and $k$. So the most you can say if you use absolute change is "it depends." –  André Nicolas May 21 '11 at 14:02

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.