A population of game ducks at a western lake contains 55 males to ever

A population of game ducks at a western lake contains 55 males to every 45 females, while a population of game ducks at an eastern lake contains 65 males for every 35 females. Among those ducks that have not yet bred there are only slightly more males than females, but among older ducks the number of males greatly exceeds the number of females. Because there are appreciably more males among adult ducks than among young ducks, we can infer that the greater the disparity in overall sex ratios, the greater the percentage of older male ducks in the population.

We do not even need the last sentence. It is inferred from the first too.

Which one of the following can be inferred from the passage?

(A) The population of game duck at the western lake contains a lower percentage of adult males than the population at the eastern lake contains.
What is good in "infer" type of question, we can find the option that is truly infered and even not to look to the other options. (You can not do it with strengthen-weaken questions).
This is correct option. We have 55% of males in WL vs 65% in EL. You can even disregard young ducks there. Because this ratio even higher for adult ducks. If I meet such question at GMAT, I think, I will skip other options.


(B) The population of game duck at the eastern lake contains a higher percentage of nonadult game ducks than the population at the western lake contains.
It is quite the opposite to A, so it is wrong

(C) The total number of male game ducks is higher in the eastern lake’s population than in the western lake population.
Common GMAT trap. We can not say anything about the total nu,ber if only the percentage is given. And it is true also for the opposite situation.

(D) The number of nonadult ducks hatched in a breeding season is higher in the eastern lake’s population than in the western lake’s population.
Same trap as in C

(E) Adult female game ducks outnumber nonadult female game ducks in the eastern lake’s population.
We do not know anything about female ducks in any lake (if we do not speak about the ratio to males).

OFFICIAL EXPLANATION

If time is tight—or you find that you cannot follow the argument as presented—this one is practically screaming, “Skip me for now; come back to me later on.” Handling it requires a firm grasp on the comparisons offered, as well as on the direct relationship that is the author’s conclusion. Let’s start with that. According to the author, one will find a higher percentage of older male ducks when there is a great disparity in sex ratios overall (i.e. all males : all females). How come? Because among older ducks there are a lot more males, whereas among younger ducks the male : female ratio is much closer to 1 : 1. In other words, the more the male ducks strongly outnumber the females, the likelier it is that the older males will outnumber the younger ones.

Compare the male : female ratio at the two lakes in question. The western lake’s is close to 1 : 1 (55 : 45), while the eastern lake’s is almost 2 : 1 (65 : 35). Which lake, according to the conclusion, should have a greater percentage of older males? The eastern—that’s the lake with the greater male : female disparity. So the western lake should have a lower percentage of older males . . . and that’s just what (A) points out.

(B) The data in the argument compare the ages of adult and nonadult males. We cannot draw (B)’s conclusion about adult vs. nonadult ducks—males and females combined.

(C) No conclusion about a total population can be drawn from a male : female ratio. Contrary to (C), the western lake could have many more male ducks than the eastern, so long as the western’s population reduces to 55 : 45 and the eastern’s to 65 : 35.

(D) introduces an issue—hatching time—that is totally removed from the argument. Hence, (D) is completely unacceptable as an inference.

(E)’s conclusion about the age ratio of adult females : nonadult females is unjustified, because no data comparing those groups are provided. The conclusion only concerns males.

We know basically two things, but they are separated in the text by a vast distance so it's hard to put them together.

1. A population of game ducks at a western lake contains 55 males to every 45 females, while a population of game ducks at an eastern lake contains 65 males for every 35 females.

2. the greater the disparity in overall sex ratios, the greater the percentage of older male ducks in the population.

With these two pieces of information we can infer that Eastern Lake is older than Western Lake.

(A) says that Western Lake is younger, which is the same thing as the Eastern Lake is older. So this is the correct answer.
(B) says the Eastern Lake is younger, which is the opposite of what we can infer.
(C) says nothing about which lake is older. Also, from the stimulus we know information about percentages, nothing about amounts of ducks. Depending on which lake was bigger the claim could be severely challenged.
(D) is out of scope. We know nothing about the ducks hatched in a breeding season.
(E) twists around the second claim we know to be true. The second claim says that the greater the disparity in sex ratios the greater the percentage of older male ducks. It says nothing of the percentage of older female ducks.

Tricky question! I analyze all from the premise, nonetheless answer is inferred only from the conclusion of the argument.

This passage will make us overwhelmed with the abundance of data on the premise. Good question!

That was a tricky question!
Took me a 3 mins, but thankfully I was spot on.

Here's my approach:

Q type: Inference.
Q stem:

For Inference questions, we have to assume that everything mentioned in the stem is completely true, including the conclusion! This was the tricky aspect.

Conclusion mentions: "greater the disparity in overall sex ratios, the greater the percentage of older male ducks in the population"
Thus, Percentage of older male ducks in Western lake < Percentage of older male ducks in Eastern lake


(A) The population of game duck at the western lake contains a lower percentage of adult males than the population at the eastern lake contains.
In line with our prediction.

(B) The population of game duck at the eastern lake contains a higher percentage of nonadult game ducks than the population at the western lake contains.
Tempting! But we have no information about percentage of Nonadult ducks

(C) The total number of male game ducks is higher in the eastern lake’s population than in the western lake population.
Out of scope: Conclusion only talks about percentages.

(D) The number of nonadult ducks hatched in a breeding season is higher in the eastern lake’s population than in the western lake’s population.
Out of scope: Conclusion only talks about percentages. Moreover, there's no mention of breeding season

(E) Adult female game ducks outnumber nonadult female game ducks in the eastern lake’s population.
Out of scope: Conclusion only talks about percentages of older male ducks.

Please do let me know if I overlooked anything!

Took me five minutes to understand that "ducks that have not yet bred" was the same thing as "young ducks".

I dont think this is obvious. What if half of the older ducks have not yet bred?

Posted from my mobile device

Definitely a difficult question. Between A and B.

But we don't have any idea about the number of non-adult ducks. Option A wins.

A population of game ducks at a western lake contains 55 males to every 45 females, while a population of game ducks at an eastern lake contains 65 males for every 35 females. Among those ducks that have not yet bred there are only slightly more males than females, but among older ducks the number of males greatly exceeds the number of females. Because there are appreciably more males among adult ducks than among young ducks, we can infer that the greater the disparity in overall sex ratios, the greater the percentage of older male ducks in the population.

Which one of the following can be inferred from the passage?

(A) The population of game duck at the western lake contains a lower percentage of adult males than the population at the eastern lake contains. - CORRECT. Less ratio of M and F in western lake compared to eastern lake suggests that eastern contains higher percentage of adult males.

(B) The population of game duck at the eastern lake contains a higher percentage of nonadult game ducks than the population at the western lake contains. - WRONG. Nonadult game ducks include both male and female. This can't be concluded though it's opposite to A.

(C) The total number of male game ducks is higher in the eastern lake’s population than in the western lake population. - WRONG. If one misread the passage this one's going to be the answer for them. Passage gives us a ratio in a deceiving language that needs attention.

(D) The number of nonadult ducks hatched in a breeding season is higher in the eastern lake’s population than in the western lake’s population. - WRONG. Irrelevant.

(E) Adult female game ducks outnumber nonadult female game ducks in the eastern lake’s population. - WRONG. Opposite.

The most difficult choice is B and rest are easy EXCEPT C.

Answer A.