#Percent #Inference

Question


From 1980 to 1989, total consumption of fish in the country of Jurania increased by 4.5 percent, and total consumption of poultry products there increased by 9.0 percent. During the same period, the population of Jurania increased by 6 percent, in part due to immigration to Jurania from other countries in the region.

If the statements above are true, which of the following must also be true on the basis of them?

(Because of copyrights, the complete official question is not copied here. You can access the question here: GMAT Club)

Difficulty: Medium

Accuracy: 66%

Based on: 3512 sessions

Solution


The Story

From 1980 to 1989, total consumption of fish in the country of Jurania increased by 4.5 percent, and total consumption of poultry products there increased by 9.0 percent. – From 1980 to 1989, total fish consumption increased by 4.5% and total poultry consumption increased by 9%.
(β€œtotal consumption” –> weight of the meat consumed. So, maybe people have started consuming more fish and poultry, or maybe the population has increased, leading to this increase in consumption.)

During the same period, the population of Jurania increased by 6 percent, in part due to immigration to Jurania from other countries in the region.– Ok, So there was a population increase. This increase was partly due to immigration. (6% is in the middle of 4.5% and 9%. Had eating trends remained the same for the entire population, food consumption should have increased by 6%. Maybe immigrants consume more poultry and less fish on average than native Juranians.)

Question Stem

If the statements above are true, which of the following must also be true on the basis of them?

We’re looking for an inference here. From the passage, I can surmise that consumption of fish went down with respect to the increase in population, and consumption of poultry went up with respect to the increase in population.

I mentioned above that maybe the immigrants consume more poultry and less fish on average than native Juranians. While that could be true, it is not something that I can infer from the given information. I can’t be sure about what would have caused these changes.

Let’s take a look at the answer choices.

Answer choice analysis


Answer Choice: A

Incorrect

Selected by: 3%

We are only given figures for the percentage increases in consumption. The passage does not discuss anything about revenues, costs or profits. Can’t infer this one.


Answer Choice: B

Incorrect

Selected by: 16%

A deceptively attractive answer choice.

I have talked about this above as well. it is certainly possible that the immigrants consumed more poultry than fish, and that eating habit was the reason for a less than 6% increase in total fish consumption and a more than 6% increase in total poultry consumption.

Remember though, our objective here is to find an answer choice that must be true on the basis of the above passage.

So, can we be certain that for the immigrants, fish was less likely to be a major part of their diet than was poultry? No.

  1. The passage doesn’t state that the population increase was solely due to immigration. Immigration was just partly responsible. May be bulk of the population increase was domestic.
  2. Even if the population increase was solely because of immigration, we don’t know what caused the respective increases in fish and poultry consumption. It is possible that there was an overall trend in the country of shifting towards higher poultry and lower fish consumption.

    Note: Some test takers get attracted to this answer choice thinking that “This could justify why the consumption of fish and poultry increased the way they did. It fits.” Our objective is not to find something that could fit, though. It is to find an answer choice we can infer. We cannot infer (B).

Answer Choice: C

Incorrect

Selected by: 3%

Sure, 9 is twice 4.5. But those figures just represent the percentage increases in consumption.

We do not have any information about total consumption in absolute terms. e.g. fish consumption could have gone up from 1000 tonnes to 1045 tonnes (a 4.5% increase), and poultry consumption could have gone up from 200 tonnes to 218 tonnes (a 9% increase). So, poultry consumption need not even be greater than fish consumption in 1989, let alone be twice as much.


Answer Choice: D

Incorrect

Selected by: 12%

Were fish and poultry products a β€œregular part” of the diet?
No idea.
All we know is that their consumptions increased by 4.5% and 9%. What were the bases for those increases? We have no clue.

True story: I consume significantly more apple cider vinegar now than I did ten years ago.
Does that mean that ACV is a regular part of my diet?
I know for a fact that it is not πŸ™‚

Consumption going up doesn’t mean that the food item is a regular part of the diet. Cannot infer this answer choice.


Answer Choice: E

Correct

Selected by: 66%

We know from the passage that fish consumption has increased. This option talks about a decrease related to fish consumption. These two pieces might seem contradictory to each other. They actually are not. The 4.5% increase in the passage deals with overall increase in fish consumption. This answer choice talks about a decrease in per capita fish consumption.

Let’s first understand what ‘per capita consumption of fish’ means.

Per capita consumption of fish = Total fish consumption by weight / Total population

The passage tells us that the numerator of the fraction has increased. This answer choice is talking about the overall fraction decreasing. Both these pieces of information could be true simultaneously. At least there is no contradiction here.

Now let’s see why we can infer it.

From 1980 to 1989, fish consumption increased by 4.5%, and the population increased by 6%. Fish consumption increased by a lower percentage than the population, therefore the per capita consumption of fish (the overall fraction) would have certainly reduced.

We can understand this algebraically too:

In 1980
Say, the total fish consumption was: F kg
Say, the total population of Jurania was: P

==> Per capita consumption of fish in 1980 =  F/P kg per person

In 1989
Fish consumption increased to: F*1.045 kg
Population increased to: P*1.06
==> Per capita consumption: F*1.045/P*1.06 kg per person
= (F/P) * (1.045/1.06)

1.045 < 1.06
==> 1.045/1.06 < 1
==> F/P * 1.045/1.06 < F/P

Thus, yes, the per capita consumption of fish was certainly lower in 1989 than in 1980.

If you have any doubts regarding any part of this solution, please feel free to ask in the comments section.

Anish Passi

GMAT Coach

With over a decade of GMAT training experience, top 1 percentile scores on the CAT and GMAT, and a passion for teaching, I’d like to believe I am quite qualified to be a GMAT coach. GMAT is learnable, and I help students master the GMAT through a process-oriented approach based on logic and common sense. I offer private tutoring and live-online classroom courses. My sessions are often sprinkled with real-world examples, references to movies, and jokes that only I find funny. You’ve been warned πŸ™‚

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