PT1, S1, Q7 - Game Duck Western Lake question

[joliebella]

At first I choose D after eliminating the answer choices. Ofcourse, it was wrong. I realize after the fact, that number of nonadult ducks hatched in a breeding season is higher in the eastern lake's population than in the Western population. I realized that this was not discussed in detail. So, I went with A and realized the first three sentences and the conclusion makes it correct. Is that correct. Can you go through the answer choices at length. Many thanks in advance.

[ManhattanPrepLSAT1]

Great question. This one is really interesting with the play on numbers and percentages.

The LSAT is not really a math test, so this is about the most math you'll get in any question in the Logical Reasoning section. The only place math might have a stronger role would be in a few Logic Games that play on various numerical distributions.

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.

I hope this clears things up for you. I'm really glad you chose this one, as I haven't seen it in a while, but I taught it in class for years.

[ManhattanPrepLSAT1]

Check out my colleague's approach as well.

prep-test-1-que-7-game-duck-question-t1082.html#p2453

[joliebella]

Many thanks, guys. Thanks sooo much!