Here we have LSAC trying to confuse you by giving you ratios, hoping you mistake them for actual numbers. Saying that the western lake contains 55 males to every 45 females doesn't mean there are 55 males and 45 females. It's giving you a ratio of 55:45, or simplified 11:9. Likewise, the eastern lake has a ratio of males to females of 65:35, or simplified 13:7. Since this is a must be true question, our correct answer will be 100% supported by the passage.
(A) This is our CORRECT answer because the western lake is 55% male, whereas, the eastern lake is 65% male. Therefore, the population of the game ducks at the western lake contains a lower percentage of adult males than the population at the eastern lake.
(B) This is INCORRECT because it is not 100% supported by the passage. We know that among older ducks, the number of males greatly exceeds the number of females (more males among adult ducks than among young ducks). However, this is a generalization on ducks as whole. We do not know the break down of adult and non-adult ducks in the eastern or western lake. Therefore, we cannot definitively infer answer choice B.
(C) This is INCORRECT because it is not 100% supported by the passage. Here is where the ratio to number flaw kicks in. We don't know the total number of male and female ducks in the different lakes. We only know the ratios.
(D) This is INCORRECT because it is not 100% supported by the passage. The passage hasn't given us any information about breeding season, and therefore, we cannot infer anything about it.
(E) This is INCORRECT because it is not 100% supported by the passage. Just like in (C), we don't actually know any total numbers. Therefore we cannot make a definitive statement on whether or not adult female ducks outnumber nonadult female game ducks in the eastern lack.
Hope that helps! Let me know if you have any more questions!
RomaJuly 3, 2013
Thank You.
josepablosalasJuly 6, 2018
How do we know they are adult? The passage just states that there are 55 males at the western lake and 65 males at the eastern lake.
Victorrodrigues01March 26, 2020
I am still confused as to why A is the correct answer because how do we know for sure that the actual numbers are higher based on percentage only. What if the western lake does have a bigger population than the eastern lake in spite of the ratio... I am a bit lost as to how based on the information in the stimulus A must be true....Help!
VictoriaSeptember 14, 2020
Hi @Victorrodrigues01,
Happy to help!
We know that the western lake has 55M to 45F and the eastern lake has 65M to 35F. Notice that both these sets of numbers add up to 100. Therefore, the western lake's population is 55% male whereas the eastern lake's population is 65% male.
Answer choice (A) says that the population at the western lake has a lower percentage of males than the population at the eastern lake. We can see from the above that this is true. The eastern lake's population has a higher percentage of males (65%) than the western lake's (55%).
In this way, actual numbers don't matter. The percentage always stays the same regardless of how many ducks are actually in the population. Even if the western population is bigger than the eastern population, the eastern population will still have a higher percentage of male ducks.
Example:
Western Lake has 1000 ducks 55% males = 550 ducks 45% females = 450 ducks
Eastern Lake has 100 ducks 65% males = 65 ducks 35% females = 35 ducks
While the western lake has more male ducks than the eastern lake, the eastern population still has a greater percentage of male ducks than the western population.
Hope this helps! Please let us know if you have any further questions.
