Last August most gasoline stations in the XT chain of gasoline station

Question

Last August most gasoline stations in the XT chain of gasoline stations participated in a temporary sales promotion that XT sponsored. In the promotion, any customers who purchased ten or more gallons of gasoline were entitled to a free car wash. For the month of August, the XT chain’s gasoline sales were five percent higher than in August the previous year. Evidently the promotion was successful as a means of boosting sales.

Which of the following, if true, most strengthens the argument?

A. During last August, some of XT’s competitors also had sales promotions in effect and also experienced sales increases as compared to the previous August.
B. The money that XT earned from the increase in gasoline sales was not enough to offset the cost of providing free car washes during the promotion.
C. Some customers who took advantage of the promotion would have made smaller but more frequent gasoline purchases at XT gasoline stations if the promotion had not been in effect.
D. XT gasoline stations that participated in the promotion but did not have car wash facilities on their premises gave vouchers that could be used at a nearby car wash.
E. Last August the XT gasoline stations that did not participate in the promotion had no increase in gasoline sales as compared to their sales the previous August.

Bunuel · Answer

Similar question from GMAT Prep Focus mocks: https://gmatclub.com/forum/last-august- ... 60887.html

guddo · Answer

Last August most gasoline stations in the XT chain of gasoline stations participated in a temporary sales promotion that XT sponsored. In the promotion, any customers who purchased ten or more gallons of gasoline were entitled to a free car wash. For the month of August, the XT chain’s gasoline sales were five percent higher than in August the previous year. Evidently the promotion was successful as a means of boosting sales. 
 
Which of the following, if true, most strengthens the argument?

The argument says XT ran a promotion at most stations and August gasoline sales increased by five percent compared with the previous August.  The key issue  is whether the increase was caused by the promotion rather than by some general factor affecting all XT stations or the gasoline market overall.

(A) During last August, some of XT’s competitors also had sales promotions in effect and also experienced sales increases as compared to the previous August.

This weakens rather than strengthens. If competitors also had promotions and also saw sales increases, XT’s increase may have been part of a broader market pattern, not necessarily caused by XT’s promotion.

(B) The money that XT earned from the increase in gasoline sales was not enough to offset the cost of providing free car washes during the promotion.

This does not strengthen the claim that sales increased because of the promotion. It concerns profitability, not whether the promotion boosted gasoline sales.

(C) Some customers who took advantage of the promotion would have made smaller but more frequent gasoline purchases at XT gasoline stations if the promotion had not been in effect.

This weakens the argument. It suggests that some customers may have simply bought the same amount of gasoline in larger individual purchases, not more gasoline overall.

(D) XT gasoline stations that participated in the promotion but did not have car wash facilities on their premises gave vouchers that could be used at a nearby car wash.

This only explains how the promotion was implemented at some stations. It does not show that the promotion caused the sales increase.

(E) Last August the XT gasoline stations that did not participate in the promotion had no increase in gasoline sales as compared to their sales the previous August.

This is correct. If participating stations were part of the chainwide increase but nonparticipating stations had no increase, that supports the idea that the promotion, not some general XT-wide factor, caused the sales boost. This gives a useful  comparison group .

Answer: (E)

vasu1104 · Answer

there is XT chain of gasoline and few of those gas stations participated in temp sales promotion.
promotion- buy 10 or more gallons of gasoline and get free car wash.
that month of august the sales were 5% higher than august of previous year.
conclusion- promotion was successful in boosting sales

so there is no other reason for increase in sales. so if we can rule any of those factors, we get out correct ans.

A this weakens the arguments since promotion was everywhere. reject.
B this has no impact on the discussion whatsoever. reject.
C so because of promotion, few made big purchase but had promotion not been there, they still would have made purchase in smaller quantity but more frequently. so this actually somewhat weakens it. reject.
D this is irrelevant here. out.
E perfect. so if the stations who did not participate had no increased in their sales, it tells that promotion was reason for higher sales in those stations where promotion was in effect. so keep.

MartyMurray · Answer

Last August most gasoline stations in the XT chain of gasoline stations participated in a temporary sales promotion that XT sponsored. In the promotion, any customers who purchased ten or more gallons of gasoline were entitled to a free car wash. For the month of August, the XT chain’s gasoline sales were five percent higher than in August the previous year. Evidently the promotion was successful as a means of boosting sales.

Conclusion:

Evidently the promotion was successful as a means of boosting sales.

Supporting premise:

For the month of August, the XT chain’s gasoline sales were five percent higher than in August the previous year.

We see that the reasoning of the argument is basically that, since XT's sales were higher when the promotion was occurring than when it wasn't, the promotion was the cause of the sales increase.

Which of the following, if true, most strengthens the argument?

The correct answer to this Strengthen question will help to confirm that the promotion was indeed the cause of the sales increase.

A. During last August, some of XT’s competitors also had sales promotions in effect and also experienced sales increases as compared to the previous August.

This choice may seem to confirm that sales promotions were the causes of the sales increases. However, in reality, it makes no difference.

After all, it just extends what we already know - there were promotions and sales increases at the same time - to competitors.

Great, but did the promotions cause the sales increases?

To confirm the connection between the promotions and the sales increases, we need something new.

Eliminate.

B. The money that XT earned from the increase in gasoline sales was not enough to offset the cost of providing free car washes during the promotion.

This choice provides only information on the net profitability of the promotion and none on whether the sales increase was actually caused by the promotion.

Eliminate.

C. Some customers who took advantage of the promotion would have made smaller but more frequent gasoline purchases at XT gasoline stations if the promotion had not been in effect.

This information may seem to affect the strength of the argument but actually makes no difference at all.

The passage states as fact that sales were 5 percent higher than sales in August of the previous year. So regardless of whether some customers changed their buying patterns in response to the promotion without changing the amount of gasoline they purchased, it remains the case that sales increased by 5 percent.

Eliminate.

D. XT gasoline stations that participated in the promotion but did not have car wash facilities on their premises gave vouchers that could be used at a nearby car wash.

This indicates only how the promotion was handled, not whether it caused the increase in sales.

After all, the fact that some stations gave out vouchers doesn't really add to what we know. We already know from the passage that there was a promotion. The fact that vouchers were used for the promotion doesn't connect the promotion to the sales increase.

Eliminate.

E. Last August the XT gasoline stations that did not participate in the promotion had no increase in gasoline sales as compared to their sales the previous August.

This choice is interesting.

After all, it shows what happens if we remove the variable of the promotion.

We already know that, with the promotion, sales increased. Now this choice tells us that, without the promotion, sales didn't increase.

In other words, without the presumed cause, there was no effect.

That information provides some confirmation that the sales increase was caused by the promotion.

Keep.

Correct answer:   E

horrorslive · Answer

i have a doubt, if anyone can help  MartyMurray   ChiranjeevSingh   GMATNinja 
Argument is saying Promotion happened--> Sales increased
ie X leads to Y

We want to strengthen it,
E. says X didn't happen so Y didn't happen. Which is correct and a strengthener

But, for option A
Example of X leads to example of Y
Isn't this also strengthener because it is supporting X leads to Y?

egmat · Answer

Hi horrorslive,

I love that you're thinking in X → Y terms; that's the right instinct for a causal argument. The catch is in what A actually gives us versus what you're reading into it.

A is not "X causes Y again" - it's just "X and Y happened together again."  Look at the exact words: competitors  "also had sales promotions in effect and also experienced sales increases."  That's the same correlation the original argument has - promotion present, sales up at the same time. It never tells us the promotion  caused  the competitor's increase. So repeating a correlation doesn't confirm the cause; it just repeats the thing we're trying to prove.

Worse, A quietly hurts the argument. If XT's rivals  also  saw increases last August, that points to a  market-wide reason  (more driving, higher demand, whatever) lifting everyone's sales - which is exactly the alternative explanation we'd want to rule out.

Why E is the real strengthener:  E removes the promotion and checks the result. XT's  non-participating  stations had  no increase . So: cause present → effect; cause absent → no effect. That's a genuine controlled comparison isolating the promotion as the driver - which is what causal support needs.

Turn one knob to feel the difference: 
- A as written: competitors had promotions  and  rising sales → suggests a shared outside cause. (Weakens.)
- Imagine instead: "Competitors who ran  no  promotion saw  no  sales increase." → now the promotion looks like the cause. (Strengthens - same logic as E.)

See how the strengthener always comes from the  contrast between cause-present and cause-absent , not from stacking up more "they happened together" cases? That's the move to lock in.

Answer: E

MartyMurray · Answer

(A) basically repeats what we know, that there were promotions and also sales increases.

So, (A) doesn't really add anything new.

After all, (A) means merely that other companies had the same experience with promotions and sales increases that XT had. OK, great, but the fact that many companies had the same experience doesn't help to confirm that the promotions caused the sales increases. It could be that something else was the cause of the increases for all of them.

dhairya18 · Answer

The Logical Problem with Option (A)

Option (A) says that competitors running promotions ALSO saw sales increases.
Ask yourself: What kind of promotions were the competitors running?

Option (A) does not say the competitors offered free car washes. They could have been offering free coffee, double rewards points, or 20% off snacks.
If every company that ran any kind of promotion saw a 5% sales jump in August, it means the sales boost was not caused by XT's specific car wash idea.
Instead, it points to a broader market trend: August was simply a month where people were buying more gas overall.
Whenever people are already driving more (e.g., lower oil prices, sunny vacation weather), every company that runs a basic advertisement or discount catches that wave of extra customers

Comparison: Why Option (E) works and Option (A) fails
To prove a Cause -> Effect relationship, you must isolate the cause:

(A) Weakens / Undermines: The market was hot in August anyway. XT's car wash didn't necessarily cause the jump—the general August surge did.

(E) Strengthens: Same company, same month, same region. The ONLY difference was the car wash promotion. This proves the car wash was the direct cause.

Last August most gasoline stations in the XT chain of gasoline station

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Last August most gasoline stations in the XT chain of gasoline station

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