Many gardeners believe that the variety of clematis vine that is most

The statement in red is where you went wrong. Popularity in this argument is defined by sales. And if you buy a plant with the intention of growing it, by definition, you're a gardener! So the most popular plant among gardeners is the one with the most sales.

If there were 8 varieties of plant, the one that accounts for 10% of the sales can't be the one with the most sales. (If sales were distributed equally, each plant would account for 12.5% of sales.)

Put another way, if there were exactly 10 varieties of plant, and sales were distributed equally, each plant would account for 10% of sales. So there must be more than 10 varieties of plant for that 10% figure to be the highest, meaning (A) must be true.

I hope that clears things up!

Many gardeners believe that the variety of clematis vine that is most popular among gardeners in North America is jackmanii. The statement talks about a belief held by many gardeners. What is the belief? Jackmanii is the most popular type of clematis vine among gardeners in North America.
This belief is apparently correct since, of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii. The author agrees with the belief based on some evidence.
‘apparently correct’: this phrase indicates that the author accepts the belief to be correct based on some piece of information.
What is the piece of information? That 10% of the clematis vines sold by the largest nursery (out a total of 1 million clematis vines sold) are jackmannii.

Author’s logic:
10% of the large number (1 million) of clematis vines sold by the largest nursery are jackmanii (basis). Therefore, jackmannii is the most popular vine of any gardeners in North America.


Gap(s) in logic:

- What’s the big deal with 10%? The author must believe that no other clematis vine sold more than 10%. There could be a vine that constituted more the 10% of the sales.
- Smaller nurseries might overshadow the largest nursery’s sales.
- Does overall sales indicate popularity among gardeners? Maybe architects order plants for landscaping without inputs from gardeners.

There could be additional gaps in the argument. I came up with these.



Which of the following is an assumption on which the argument depends?

We’re looking for an assumption. ‘an assumption on which the argument depends’: this wording implies that we are looking for a statement without which the argument would not make any sense. Thus, one test we can apply while going through the answer choices is: does the argument still remain valid if we add the negation of the answer choice to the context. If it does, then the argument would not be dependent on the answer choice, and thus the choice would be incorrect. Also, an assumption is something that the author would have needed to make the argument. So, assumptions support the argument. If we find an answer choice that weakens the argument, it cannot be an assumption.

Prediction:
The author assumes that:

10% is the highest portion
The sales of the largest nursery are representative of overall sales
Popularity of a vine among gardeners can be determined on the basis of sales in nurseries

A. The nursery sells more than 10 different varieties of clematis
Correct. What is the author’s logic?
Since 10% of the vines sold by the largest clematis nursery were jackmanii the most popular such vine is jackmanii.
When would 10% be a big deal?
When no other vine sold 10% or more.
Now, if the nursery sells 10 or fewer varieties (negation), then 10% jackmanii sales would not be the single largest proportion. So, the author’s logic falls flat.

For the author to conclude that jackmanii is the most popular vine variety among gardeners on the basis the 10% figure of the largest nursery, the author must have assumed that 10% is the highest proportion of sales by any clematis vine variety.

Let’s use a bit of math to understand why this answer choice is correct.

Say, the nursery sold 9 varieties of clematis vines. Even if each variety sold equally, the proportion of sale would be 11.11% each. If any variety sold more than the others, its proportion would be even higher than 11.11%. And if there was actually a vine which was responsible for >10% of the sales, then the author would not have concluded that jackmanii is the most popular on the basis of its 10% sales figure.

So, had there been 10 or fewer clematis vine varieties sold at the nursery, at least one variety would have sold a proportion higher than 10%. That would destroy the argument’s logic.

Why does the author believe that jackmanii is the most popular clematis vine on the basis of the 10% figure? The author must assume that 10% is the highest proportion among all clematis vines. That would only happen if the total number of vines is more than 10.

Note: I find many test-takers eliminate this answer choice in their first-go, and only come back to it after eliminating all the others. To understand why this answer choice is correct requires a deeper level of quantitative reasoning than most CR questions. (I talk more about this answer choice in the additional notes at the bottom.)


B. The largest clematis nursery in North America sells nothing but clematis plants
Incorrect. Statement: The nursery does not sell any plants other than vines.

If this statement were true, then maybe the nursery is indeed a reliable source to understand which vine is the most popular vine among gardeners. i.e., the answer does support the argument mildly. However, for the argument to hold true, is it necessary for the nursery to not sell other plants? What if it did? What if the nursery did sell plants in addition to clematis vines (negation)? Even then, as long as it is the largest clematis vine nursery in North America, the argument’s logic remains intact.

It helps to be clear that the 10% sales are of ‘the one million clematis plants sold per year’ and not of the total number of plants sold per year by the nursery.



C. Some of the jackmanii sold by the nursery are sold to gardeners outside North America
Incorrect. What impact does this answer choice have on the argument? The conclusion of the argument is that that the belief that jackmanii is the most popular clematis vine among gardeners in North America is correct. If some of the jackmanii sold by the nursery are sold to gardeners outside North America, my belief in the conclusion reduces. This answer choice weakens the argument, thus cannot be an assumption.

We can also evaluate this answer choice by checking whether it is necessary for the argument. What if none of the jackmanii sold by the nursery is sold to gardeners outside North America (negation)? In that case, our belief in the argument goes up. The negation of the statement supports the argument instead of breaking it down. Thus, this answer choice is incorrect.

I find that many people reject this answer on the basis of the word ‘some’.

Let’s replace the word ‘some’ with the word ‘most’.

Most of the jackmanii sold by the nursery are sold to gardeners outside North America.

Does this change make this answer choice correct?

If most jackmanii sold by the nursery are exported outside NA, the argument gets weakened. We would then believe less in the point that jackmanii is the most popular clematis vine in NA.

If a statement weakens the argument, it can’t be an assumption. The author would not have assumed something that weakens the argument.

Thus, the reasoning that this answer choice is not an assumption because it mentions the word ‘some’ is flawed. ‘some’ or ‘most’, the answer choice weakens the argument, and thus is not an assumption on which the argument depends.


D. Most North American gardeners grow clematis in their gardens
Incorrect. The argument is based on the nursery’s sales.

Gardeners could buy from a nursery and grow clematis in their gardens, or they could plant from scratch and grow clematis in their gardens. In the former case, I do not learn anything about categories within clematis. Thus, the statement becomes irrelevant for the argument. In the latter case, the argument actually gets weakened. If most gardeners plant clematis from scratch in their gardens, the sales data of the largest clematis nursery would not really mean much with regards to which clematis vine is the most popular among gardeners.

Thus answer choice either is irrelevant or weakens the argument. Either way, it is not necessary for the argument that most gardeners grow clematis in their gardens. Even if most didn’t (negation), the argument’s logic still remains intact.



E. For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.
Incorrect. Tricky one. This answer choice does strengthen the argument. If for all clematis-specializing-nurseries, at least 10% of the clematis plants sold are jackmanii, I certainly start to believe more that jackmanii is the most popular clematis vine variety among gardeners in North America.

Is the statement necessary though?
Is it absolutely necessary for the argument that all ‘specialist’ nurseries sell such a proportion of jackmanii?
What if even one nursery (perhaps a small one) sells a smaller proportion of jackmanii than 10% (negation)? Does the argument break down then? No, it doesn’t. The argument still makes sense even if few specialist nurseries sell less than 10% jackmanii.

Remember, we are looking for an assumption on which the argument depends.

Does the argument depend on this answer choice?
In other words, is it absolutely necessary for all such nurseries to at least 10% of their clematis sales through jackmanii?
No.




FAQ – related to answer choice A:
Even if there are more than 10 varieties of clematis vines, it isn’t necessary that 10% is the highest share. Another vine might still have sold more. Then shouldn’t option A be wrong?
There is a flaw in this reasoning. When we are looking for an assumption, we are looking for something that is necessary for the argument to make sense – i.e., without which the argument should not make any sense. However, we are not looking for something that makes that argument logically foolproof. In other words, an assumption would be necessary for the argument, but it need not be sufficient.
The above-mentioned reasoning simply states that we may not be able to reach the conclusion even if we add option A to the argument. And that’s fine. Option A is necessary – i.e., if there are 10 or fewer varieties in the nursery, then the argument’s logic gets shattered. Option is not enough (sufficient) – i.e., even if option A is true, it is possible that the conclusion may still not follow.
This distinction between necessary and sufficient is quite helpful in dealing with assumption questions. I see test-takers make two kind of mistakes in this context:

1. Eliminate the correct answer because it isn’t sufficient, even though it is necessary
2. Select an incorrect answer because it is sufficient (i.e. it confirms the conclusion), even though it is not necessary

Hi avigutman - still not a 100 % comfortable on answer choices that are necessary but not sufficient. I think most answer choices on the GMAT are necessary and sufficient ?

Would this be an example of a assumption that is BOTH necessary and sufficient ?


I think option F is both necessary and sufficient, but not sure.

Reason i say that is -

Had option F been in place of option A in the original question -- most people including me would very easily have spotted option F as an assumption

Trying to understand why my option F is so easy to spot as an assumption but option A is much harder to spot as an assumption.

I think its because option is BOTH necessary and sufficient but not sure.

Just curious on your thoughts

No, jabhatta2. F is still not sufficient, because we don't know what's happening in all the other nurseries in North America. But A is even more insufficient.
Generally speaking, GMAT assumptions are almost never sufficient.

The word "depends" implies that we're looking for a necessary assumption. In theory, that necessary assumption might happen to also be sufficient, but that's extremely rare on the GMAT.

Here's an analogy:
x^2 > 25, therefore x>10
Which of the following is an assumption on which the argument depends?
(A) x is positive

A is correct, even though it's still entirely possible that the conclusion is wrong. Why, then, is A correct?
Well, if we were to discover that x is not positive, then the logic of the argument becomes nonsensical. The only reason someone concluded that x>10 is because they assumed that x lives to the right of zero. Discovering that it doesn't renders the argument's logic ridiculous.

Similarly, in the original problem, the author concludes that the variety of clematis vine that is most popular among gardeners in North America is jackmanii. Based on what? Well, based on the fact that of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii.
Are we supposed to be impressed by this statistic? 10% doesn't sound like a winner to me.
Indeed, if we discover that the nursery sells no more than 10 different varieties of clematis, 10% would for sure be a small fraction, relatively speaking. There would have to be another variety that outsells jackmanii. This is a quantitative reasoning inference, and it renders the argument's logic ridiculous.

What a clear explanation, thanks AnishPassi.
I would also like to thank other experts such as GMATNinja and avigutman for their posts.

The reason why the option (A) is correct has been fully elaborated by experts, so I want to focus on the option (C) and (E)-- they were tempting and confusing to me when I practiced this question.

There is a gap in logic in the original passage: we cannot be sure whether the sales of the largest nursery in NA is representative of the overall sales in NA, and we even do not know whether the customers buying Jackmanii at the largest nursery are gardeners in NA. Surely, it is possible that the nursery's most customers are gardeners in NA, but it is also possible that the nursery concentrates on export business and most of its clients are foreigners.

This question would be much easier if it asked us to weaken the argument--I already came up with two pieces of evidence destroying the link between the premise and the conclusion. But unfortunately, this is an assumption question.

Let's check the option (C):

c.some of the jackmanii sold by the nursery are sold to gardeners outside North America

This points out a hole in the premise (sales of the nursery) and the conclusion (the preference of gardeners in NA), so it looks quite "relevant" at the first glance. It actually tempted me as I felt that we do need an assumption addressing who the customers are. But later I realize that the assumption we need is "Not all of the jackmanni sold by the nursery are sold to gardeners outside NA" instead of the option (C). If the assumption in boldface is negated, it will destroy the argument--since all the nursery's jackmanni are sold to foreign gardeners, how well the variety is sold or whether it is the one with the best sales among all varieties at the largest nursery is irrelevant to whether gardeners in NA loves the variety the most.

As some experts have pointed out, the negation of the option (C) is "none of the jackmanii are sold to gardeners outside NA," which actually strengthens the argument. That is not what a proper assumption does--a negated assumption should wreck the argument.

And let's check the option (E):

e.For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

At the first glance, this option seems highly "relevant" to the argument--it and the conclusion look like twins! The conclusion says that the sales of jackmanii at the largest nursery makes up 10 percent of all sales of clematis plants, and the option (E) adds that the sales of jackmanii at all nurseries in NA that specialize in clematis plant also account for at least 10 percent.

I felt that it kinds of strengthens the argument, but (1) this is not a strengthener question; (2) it still does not address the importance of 10 percent--what is the link between 10 percent and "the most popular variety"? (3) after negated, the option (E) does not wreck the argument. Perhaps, in one of the nurseries that specialize in clematis, the sales of jackmanii is less than 10 percent, but so what? Maybe the nursery plants more than 20 varieties of clematis plant, and the sales of jackmanii makes up 9 percent, which is still higher than others. Or, jackmanii is less popular than another variety in one nursery but it is the most popular variety in most nurseries.

Good points, GraceSCKao. And, I’m glad you liked my solution Thank you.

One thing sticks out in your explanation for answer choice E.


My question: So what?

P.s. I’m not entirely sure what you mean by the word “address” here.

Hi GraceSCKao, good analysis! One thing that really helps me on this question type is constantly asking myself, as I read each answer choice, "is this really NECESSARY?" "do I really absolutely require this to be true in order for the argument to be a sensible argument?"

Thank you avigutman for your response.
I learned a lot with your YouTube videos. (Actually, I picked up this question in your CR video! ) Sometimes I just get confused or feel tempted at those which seem "highly relevant" to the argument, and in most cases I still need to rely on the negation skill to find the correct option. Also, I cannot answer CR question fast. I think I just need more practice.




Really like your explanation AnishPassi. It is clear. Most CR questions are cleverly designed and wrong options are wrong for good reasons, so I appreciate concise but detailed explanations, like yours.

By using the word "addressing," I meant "deal with or give attention to." The reason why 10 percent is good enough for us to accept the belief that jackmanni is the most popular variety is never explained by the author of the passage. In some competitive markets, 10 percent could indeed be the highest market share, but in some less competitive markets, 10 percent could mean the third place or the fourth place. This is a gap and only the option (A) addresses it.

To be fair, this passage has several gaps, so we cannot be really sure which gap the correct option would address before we read the options. But, like the conclusion, the option (E) implies that 10 percent is a very good figure. But we are never given an explanation why 10 percent is good. So, if we choose (E), we will continue to live with the hole.... This is why I said in my previous post that the option (E) is suspicious as it still does not address why 10 percent is good.

Thank you for your question --I feel more clear about this question after writing the above response.

Hello GMATNinja Sir - Long time no see!

How do you differentiate quantitively between the word: "Apparently" and "Definitely"?

Is it like "Definitely" = 100% & "Apparently" = 0-100% (It could be true but not necessarily 100% true), most CR problems are more so like Math/Logical problems and thus I am raising this question, thanks!

Welcome back!

That's fair, though I'd define "apparently" as "seems to be true." So while you're right that the probability is somewhere between 0 and 100%, there's reason to believe that the statement in question is true. (If I write "Apparently, Tim can fly," I'm not saying the same thing as when I write, "Tim might be able to fly," though there's some uncertainty in both cases.)

So I'd worry less about quantifying the language than about reading it precisely.

I hope that helps!

avigutman GMATNinja GMATNinjatwo can we reject choice E based on the fact that it talks about 'all' nurseries and the passage's conclusion depends on only the 'largest nursery'? If the author is concluding something based on one specific source of data, can we assume that the data derived from multiple sources (>1 nursery) will also hold rue for an assumption?

Also strangely enough, i have a doubt in B. If they sell only non clemantis plants besides jackmanii, then of course it does not make sense to say that Jackmanii is the most popular "among clemantis plants" because they would not be selling clemantis plants besides Jackmanii at al in the first place so they have nothing to compare that to.

Hi Elite097, I'm not 100% certain that I'm correctly digesting your doubts, but I will do my best to address them. Please let me know if I misunderstood or if you have follow-up questions.
Regarding your first doubt: no, we shouldn't assume that something is going to be true of all data points just because it's true of one data point. Having said that, I can definitely get behind a strategy to reject E after only reading the first three words: the author's reasoning doesn't require that anything be true of ALL nurseries. The glaring hole in the author's reasoning is that ten percent feels kinda small, and information about ALL nurseries, while possibly helpful, isn't going to be necessary.
Regarding your second doubt: I think you may have misunderstood the details of this premise:
of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii.
The ten percent isn't out of the total sales of that nursery - it's ten percent of the clematis plants sold by that nursery. Does the nursery sell non-clematis plants too? We don't care, because the 10% of clematis is independent of whether there are non-clematis plants being sold there.

avigutman 1. Ok so can we reject E for this reason that choice E talks about "all nurseries" whereas the passage is only talking about "largest nursery" and we do not need info about all nurseries to conclude somethign about largest nursery?

2. Hence I am saying that choice B is implying that only jackmanii is grown along with non clemantis plants so clearly there are no other clemantis plants as per B so how can we say Jackmanii is the most popular "among clemantis" when as per B, there are no other clematis plants

Careful, Elite097, with using the word something. what you're saying here is very different from what I said here:

This argument has a very nuanced, very specific line of reasoning, and with this particular reasoning I can't imagine why it would be necessary to know anything about all nurseries. I am not saying that, in general, one can eliminate an answer choice that appears to talk about something other than the argument's subject. If the argument claimed, for example, that the largest nursery has more than 50% of the market share, I can definitely imagine a necessary assumption about all nurseries.

Here is choice B
I suspect that your comprehension of this sentence is off. If I understand you correctly, you're reading choice B as if it said:
The only type of clematis plant that the largest clematis nursery in North America sells is Jackmanii nothing but clematis plants
But, that's not what choice B says. It's saying that this nursery only sells clematis plants (some of which are Jackmanii, and some are other types of clematis plants).

Replying to a PM:

I believe this question is about my explanation for option E:

(Adding the relevant bits here.)



When you say "double negating", the sense I'm getting is that you're perhaps thinking about "where should I add a 'not' to negate the statement."

And, do you mean that by adding two negatives we are back to where we started from? If so, no.


The goal is to negate the whole statement. I.e., to say that the initial idea is not true.


Let me explain with another example:

Statement: All Indians speak at least 2 languages.

Me: That's not true.

i.e., it is not true that all Indians speak at least 2 languages.

i.e., some Indians speak fewer than 2 languages.


“Double negative” or not, the last statement is the negation of the main statement.

Does that make sense?