[email protected] wrote:Maria won this year's local sailboat race by beating Sue, the winner in each of the four previous years. We can conclude from this that Maria trained hard.

The conclusion follows logically if which one of the following is assumed?

A. Sue did not train as hard as Maria trained.

B. If Maria trained hard, she would win the sailboat race.

C. Maria could beat a four-time winner only if she trained hard.

D. If Sue trained hard, she would win the sailboat race.

E. Sue is usually a faster sailboat racer than Maria.


The given OA is C. I did not understand the difference between the options B and C really...

Hi!

What's the source of this question? It sounds a LOT more like an LSAT question than a GMAT one. If it's from an LSAT source, then I'd advise that you completely ignore it, since the difference between sufficiency and necessity is rarely tested on the GMAT.

**FEEL FREE TO STOP READING NOW!!**

Warnings out of the way, let's break it down!

First, as always, let's start with the question stem:

The conclusion follows logically if which one of the following is assumed?

Please note that this isn't your usual assumption question (another reason why I suspect this is from the LSAT); assumption questions usually ask us for a necessary assumption, i.e. something that must be true in order for the conclusion to make sense. However, this question isn't asking us for a missing but necessary piece of evidence; it's asking us for a new piece of information that, IF assumed, proves the conclusion.

In other words, the question is really asking:

Which of the following, if true, proves that Maria trained hard?

So, we're looking for a choice that, when we add it to the evidence that Maria beat Sue, convinces us that Maria MUST have trained hard.

Now let's look at B vs C.

B) If Maria trained hard, she would win the race.

Does this prove that Maria MUST HAVE trained hard? No - just because training hard is one way to win the race doesn't mean that it's the ONLY way to win the race. For example, maybe Sue broke her leg at the starting line. Since (B) doesn't eliminate other possible paths to victory, it doesn't PROVE the conclusion.

C) Maria could beat a four-time winner ONLY IF she trained hard.

Well, we know that Maria beat Sue, a four-time winner. If we add in a new piece of evidence that the ONLY WAY to do so is to train hard, then it MUST BE TRUE that Maria trained hard. Accordingly, (C) proves the conclusion.