GMAT Strategy

Hi !

Thanks for the great flash cards.

I am not sure if this is a mistake.

On page 65, bottom left hand corner flash card, the example is
"Since Mieko's average speed was 4/3 of Chan's, her time was 4/3 as long."

Do you mean to say Mieko's average speed was actually 3/4 of Chan's, hence her time was 4/3 as long?

valleeny wrote:Hi !

Thanks for the great flash cards.

I am not sure if this is a mistake.

On page 65, bottom left hand corner flash card, the example is
"Since Mieko's average speed was 4/3 of Chan's, her time was 4/3 as long."

Do you mean to say Mieko's average speed was actually 3/4 of Chan's, hence her time was 4/3 as long?

Well, unfortunately, I have not looked at Eric's cards yet but I can tell you that that sentence is wrong. Without knowing the rest of the problem, there are two possibly correct versions of this sentence:

"Since Mieko's average speed was 3/4 of Chan's, her time was 4/3 as long."

or

"Since Mieko's average speed was 4/3 of Chan's, her time was 3/4 as long."

Of course, I am assuming that the pronoun "her" is replacing "Mieko" and not "Chan".

Rate and time are always inversely related.

Hi Eric,

I was just scrolling through your flashcards. Thanks for sharing them. They seem excellent, I will dig deeper into them soon, but I had a quick question while I was scrolling.

Your flash card regarding "Backsolving" stated:
"Start with Choice 'E' and work back to 'A' when backsolving from the answer choices"

Can you please tell me why you chose this?
From Veritas, I heard to start from C, because then you know which way to go (whether up or down).
From Kaplan, I heard to start from B or D, because if you pick the right one, you might be done. I found this might not be as good as Veritas' way.

And then I read your's, if you start from the lowest or highest, wouldn't you end up doing most amount of work?

Thanks

DestroyTheGMAT wrote:Hi Eric,

I was just scrolling through your flashcards. Thanks for sharing them. They seem excellent, I will dig deeper into them soon, but I had a quick question while I was scrolling.

Your flash card regarding "Backsolving" stated:
"Start with Choice 'E' and work back to 'A' when backsolving from the answer choices"

Can you please tell me why you chose this?
From Veritas, I heard to start from C, because then you know which way to go (whether up or down).
From Kaplan, I heard to start from B or D, because if you pick the right one, you might be done. I found this might not be as good as Veritas' way.

And then I read your's, if you start from the lowest or highest, wouldn't you end up doing most amount of work?

Thanks

Logically speaking, starting from B or D is the score-maximizing and time-saving approach.

If you start from C, then unless the answer is actually C, it is guaranteed you will have to check another answer choice. On the other hand, if you start from B, and B is too large, then you know the answer is A. In other words, by starting at B, you have a chance of selecting the right answer without doing more work even if the answer is not B. But let's say you start from B, and it is too small. Then, check D; if D remains too small, you know the answer is E while if D is too large, you know the answer is C (b/c remember B was too small). In other words, starting at B or D is, logically, the best backsolving approach.

Thanks Testluv! Makes sense. Which company do you instruct for?

DestroyTheGMAT wrote:Thanks Testluv! Makes sense. Which company do you instruct for?

Well, just look at my signature!

Thanks Eric.
Well then combining your and Kaplan's strategies together, the best way to go is answer D.

beatthegmat wrote:Thanks guys. I think there are definitely different rules of logic that apply to backsolving. I believe when I wrote that card I was influenced by a lesson I heard somewhere that problems designed for backsolving are naturally created to waste a test takers time. Thus, if a person is naturally inclined to work from first answer to last (like working through a list), then the correct answer would tend to appear at the bottom of the list.

This is at best a hypothesis, and certainly a controversial issue. Not sure I've seen a perfect answer for backsolving strategy to date!

But thanks Testluv for sharing your two cents!

Hi Eric,

Thanks for the clarification.

I agree there are different approaches to backsolving, and strategies in general always have to be matched with the particular test-taker's proclivities and inclinations. But other things equal, in fact, starting at B or D is the best approach when the answer choices are arranged in order, and when management of the problem benefits from thinking about smallness and largeness. On the other hand, there are many situations where it makes most sense to backsolve from the answer choice that is easiest to evaluate, regardless of whether it is A, B, C, D, or E. And in many situations, because of the nature of the probelm, management of the problem won't really benefit from thinking about relative size, but will still benefit from using the answer choices.

However, there is another strategy (distinct from pure "backsolving") that involves starting from the bottom answer choice. In PS, when the question stem says "which of the following?" the test-maker knows that the majority of test-takers will start from A, then check B, then check C and so on. However, the test-maker also knows that, in these situations, many test-takers will get frustrated b/c of the time investment, and will pick either A, B or C (that is, they will pick A, B or C more than 60% of the time), and exit the question. Therefore, in these situations, the test-maker is more than 40% likely to make the correct answer D or E. Accordingly, in PS, if the question says "which of the following" and you are not sure what the correct answer is, and therefore you are going to evaluate the answer choices, begin by evaluating the bottom answer choices: E, and then D, etc.

BTW, since my last post, encouraged by the fact that there have been 100, 000 downloads, I took a look at the flashcrds, and I must say, they appear to be very helpful. Also, the excel sheet you put together where the student takes notes on each question is simply awesome!

beatthegmat wrote:Hey Testluv,

I'm starting to come around to your opinion about backsolving. How would you convey your perspective on backsolving briefly in a flashcard? Just 'Start with B or D'?

And thanks for the kinds words about these flashcards and GMAT Practice Grid!

Hi Eric,

Something like this: "if the answer choices are numbers (rather than variables or expressions), and the algebra set-up is difficult and/or long-winded, consider backsolving from the answer choices. 90% of the time, the answer choices are arranged in ascending order (and even if they aren't you can always arrange them yourself!). Think BRIEFLY (no more than 5 seconds) about whether the answer should be relatively large or relatively small, and then backsolve from B or D accordingly."

I hope that is brief enough. If you want, the flashcard can also include guidance on what to do if B is too large (select A), or if B is too small (check D), but then of course the flashcard will get bigger. If you wish, I can pm to you some text that includes all of the important details, I can make it concise as possible, and then you can edit it down if you want to make it smaller. If you also want to include a sample problem applying the backsolving approach, let me know!

But I don't think this means that you have to get rid of your current backsolving flashcard; I think that is a different flashcard b/c that is a different strategy, and so just change its title from "backsovling" to somethinhg like "WOTF/start from the bottom approach":

There are many questions (in PS, CR, and RC) that aren't really "true" multiple choice questions b/c they can be answered without reference to the answer choices, and therefore, could have been asked on a written-answer, "show-your-work" exam. Then, there are some questions for which it is necessary to refer to the answer choices; these are what I call "true" multiple choice questions. All of this can, for the test-taker, be summed up in the following Kaplan strategy:

"In PS, when a question read "which of the following" (WOTF), if you don't know the answer and you are going to refer to the answer choices, be partial to the latter choices".

Note that this strategy is applicable only to PS. Although the true/not-true MC question distinction also applies to CR and RC, there it doesn't mean we should start from the bottom. Instead, it effects the specificty of our prediction. Take RC, for example. A global question that ask for the author's purpose in writing or main idea is clearly not really a multiple choice question b/c it could have been asked on a written-answer exam (no need of answer choices). Therefore, our prediction would be very specific (basically your prediction should be the answer you should have written down had the question been asked on a written-answer exam). But, consider a question that asks you: "which of the following, if true, would most strengthen the view of the critics as it is described in the second paragraph?". To answer this question, it is necessary to consult the answer choices, and the question could not have been asked on a written-answer exam. Therefore, here, our prediction would be more general, a prediction of the behavior of the correct answer: "the critics in the second paragraph think it is not a good idea to use computer-generated visual displays in courtrooms b/c it might wrongly affect the jury's perceptions--> b/c this is a strengthen question, I am looking for some answer choice that will make this argument more likely to be true."

Regards,

Testluv

Have considerably edited my post. Will send an example problem shortly! And sorry for making the post overly-long.