Question about proportionality

[noravoningersleben]

Hi all,

I have a question about proportionality versus direct proportionality:

Say, the question stem of a DS problem tells me that the revenue of a store increases proportionally to the store's sales. Last year's sales were $500,000 and revenues were $100,000. The question is: How much were this year's revenues?

If Statement (1) then tells me that this year's sales were $2 million (i.e. 4 times last year's sales), can I assume that revenues have also increased by a factor of 4 (i.e. revenues this year are $400,00)? Or could I only draw this conclusion if I were told that sales and revenues are directly proportional? I.e. could it be that since sales and revenues are not directly proportional (or at least we're not told that they are), sales this year have also increased but not necessarily by a factor of 4, making Statement (1) insufficient?

Thanks in advance for your help!

[hisabness]

Hi all,

I have a question about proportionality versus direct proportionality:

Say, the question stem of a DS problem tells me that the revenue of a store increases proportionally to the store's sales. Last year's sales were $500,000 and revenues were $100,000. The question is: How much were this year's revenues?

If Statement (1) then tells me that this year's sales were $2 million (i.e. 4 times last year's sales), can I assume that revenues have also increased by a factor of 4 (i.e. revenues this year are $400,00)? Or could I only draw this conclusion if I were told that sales and revenues are directly proportional? I.e. could it be that since sales and revenues are not directly proportional (or at least we're not told that they are), sales this year have also increased but not necessarily by a factor of 4, making Statement (1) insufficient?

Thanks in advance for your help!

you're complicating this for no reason,

[Ben Ku]

When we say that two things are proportional, we mean (by default) that they are directly proportional, or directly related. It's only different if the question says the things are inversely proportional.

When two things are proportional, we mean they are in the same ratio. We can either write it this way: S = kR, or S/R = k. So we just need to keep the ratio of Sales to Revenue constant. If we multiply one by 4, then the other is also multiplied by 4. Hope that makes sense.

[Kweku.Amoako]

btw : is sales not equal to revenues ? what is the difference ?

do you mean "profit & revenue" or "sales & revenue"

[Ben Ku]

btw : is sales not equal to revenues ? what is the difference ?

do you mean "profit & revenue" or "sales & revenue"

The original question differentiates between sales and revenues:

Say, the question stem of a DS problem tells me that the revenue of a store increases proportionally to the store's sales.

so in approaching this problem, I really don't care what the difference between sales and revenue is.

Generally speaking, Revenue is all the money a company receives, from sales or from other sources. Sales is one specific source of revenue.

[kouranjelika]

General question, how often do Prop questions appear? Is it worthwhile practicing a bunch of these?
If so, where would one find a comprehensive list of these types of questions? Also I didn't think the SG explained the subject well, does anyone have like a generic method or can someone quickly explain how to set up the proportions?

I tend to get scarred by this and I think it's for no good reason, just wasn't introduced to the concept properly.

[RonPurewal]

General question, how often do Prop questions appear? Is it worthwhile practicing a bunch of these?

I've seen maybe one or two of them, out of well over a thousand official problems. So, I guess, it would be somewhat like playing the lottery.

If so, where would one find a comprehensive list of these types of questions?

Personally, I would just google "direct proportion practice problems", or something similar.
As long as you're looking for practice on a generic math concept"”i.e., not GMAT-specific stuff"”practice problems tend to be pretty thick on the ground.