please remove

[jmuduke08]

mods please delete

[tim]

in general, don't plug in numbers unless you are absolutely sure it's safe to do so. in particular, if they give you any exact numbers in the problem (as they did here with the number 20), you cannot plug in numbers.

furthermore, you should NEVER plug in numbers on data sufficiency unless you are prepared to do one of two things:

1) test as many numbers as you need to be absolutely sure of sufficiency (and sometimes there is no way to be sure unless you test EVERY possible number)

2) arrive at two DIFFERENT answers and thereby prove insufficiency

in other words, if you ever plug in numbers on a DS problem and decide something is SUFFICIENT, you have made a mistake unless you have covered your bases - either by finding a convincing pattern or by plugging in every number that could possibly be plugged in.

[jmuduke08]

can you walk me through your approach to solving this problem as well? my apologies i didnt ask that in the original. thanks again for your help.

[sfbay]

there is a general rule about Ratios not providing enough information for hard number unless there is a relationship given between the ratios and numbers.

one of the moderators will put this into more understandable terms (I hope)

male to female say is 1:2. can be any number of males and females as long as they obey the rule. but if told something like there are 60 total then can get a hard number.

in this problem we are given bunch of different ratios and a relationship between number M and F but no link between ratios and numbers.

[jnelson0612]

there is a general rule about Ratios not providing enough information for hard number unless there is a relationship given between the ratios and numbers.

one of the moderators will put this into more understandable terms (I hope)

male to female say is 1:2. can be any number of males and females as long as they obey the rule. but if told something like there are 60 total then can get a hard number.

in this problem we are given bunch of different ratios and a relationship between number M and F but no link between ratios and numbers.

That is absolutely correct, and I think that you explained things very well.

[jnelson0612]

can you walk me through your approach to solving this problem as well? my apologies i didnt ask that in the original. thanks again for your help.

One thing that may help you going forward is to remember that your orientation in Data Sufficiency should be to attempt to prove the statements insufficient. Approach the statements with the mentality of "let me see if I can determine that this is not enough".

You certainly could have plugged in numbers, but if you have the mission to show that the statements aren't sufficient, you would have used two sets for each statement. Then you could show that the statements are not sufficient.

An even quicker way is described by the poster above: keep in mind that you can't get hard values from relationships. Then you can realize that we cannot find the value we are seeking.

[RonPurewal]

just to clarify --

One thing that may help you going forward is to remember that your orientation in Data Sufficiency should be to attempt to prove the statements insufficient.

this is true if you are taking the number plugging / "testing cases" approach to a data sufficiency problem.
that's because, when you are testing cases, "not sufficient" is a concrete result - i.e., you get 2 tangibly different answers to the prompt question from 2 different cases. on the other hand, "sufficient", in testing cases, is merely the failure to find those 2 different cases.

on the other hand, if you are doing algebra, then you will normally be trying to prove the statements sufficient, e.g., by trying to get some key expression and/or simplified numerical answer to condense out of the algebraic work.

taken together, these observations show why it's so important to master both methods.
* algebra can prove that things are sufficient, but can't really prove that they are not sufficient (you can just fail to get a sufficient answer).
* testing cases can prove that things are not sufficient, but can't really prove that they are sufficient (although you can trust patterns, and/or you may be able to test every possible case).
* together, they can do it all!