Data sufficiency ratio application

[oreoandmilk2004]

From the FDP guide, I noted that for data sufficiency:
The percent change would be sufficient if the ratio of any two of the following are given: original, change, and and new. No actual
Amount is needed. This is because we have a linear equation for original+change = new.

Would we be able to apply this data sufficiency method to any other linear equation relationship of any variable linked in the same way (I. E. price = cost + markup). In a way, if given the ratio of any of two out of three (selling price, cost, markup), then, we can determine the third variable, yet not the actual amout right? since ratio does not lead to the actual amount.

Would i be able to draw links of this percent change technique to other topics? That is essentially what I am tryin to get at.

Thank you!!

[jnelson0612]

From the FDP guide, I noted that for data sufficiency:
The percent change would be sufficient if the ratio of any two of the following are given: original, change, and and new. No actual
Amount is needed. This is because we have a linear equation for original+change = new.

Would we be able to apply this data sufficiency method to any other linear equation relationship of any variable linked in the same way (I. E. price = cost + markup). In a way, if given the ratio of any of two out of three (selling price, cost, markup), then, we can determine the third variable, yet not the actual amout right? since ratio does not lead to the actual amount.

Would i be able to draw links of this percent change technique to other topics? That is essentially what I am tryin to get at.

Thank you!!

Great question! Why yes, you could. For example, let's say that we learn that Markup/Price = 1/5. So a Price has 5 parts for every 1 part Markup. Well, if Markup + Cost = Price, then Cost must be 4 parts. So Cost/Price = 4/5 and Markup/Cost = 1/4.

And yes, you absolutely can determine relationships but not actual values. Be very careful with this on DS (and on some Critical Reasoning questions as well!); the GMAT likes to try to get you to think that you do know actual values when you don't.