understanding ratios & percentage effect

[naija_moon]

Suppose I have a scenario where x = num/denom
A model suggests that there’s a relationship where a 1% increase in the denom or a 1% decrease in the num would result in x falling by 1.8%.
How would I simplify that to calculate what % effect an overall change in the ratio of num/denom cause on x?

Thanks for any help

 

[lev888]

1% decrease in num: 0.99*num

(0.99*num)/denom = 0.99*(num/denom) = 0.99*x, which is x decreased by 1%. Where do you get 1.8%?

 

[naija_moon]

Hi thanks for coming back quickly.

Im confusing things by oversimplyfying a broader model. Essentially what i'm trying to understand is if for example a numerator is increased by 10% and denominator is decreased by 5%, is there way of calculating what the overall percentage change of the ratio would be?

 

[Dr.Peterson]

Suppose I have a scenario where x = num/denom
A model suggests that there’s a relationship where a 1% increase in the denom or a 1% decrease in the num would result in x falling by 1.8%.
How would I simplify that to calculate what % effect an overall change in the ratio of num/denom cause on x?

Thanks for any help

This doesn't make much sense. First, a 1% increase in d and a 1% decrease in n will not have the same effect, and neither would decrease the ratio by 1.8%. Second, if x is the ratio n/d, then a change in the ratio is the same change in x.

I think you are asking a counterfactual hypothetical question, and you need to state the actual, specific question you have in mind. That may help you to say what you really mean.