A population of game ducks at a western lake contains 55 males to every 45 females, while a population of game ducks ...

Hello, I am having trouble seeing how this argument is valid. As I was answering the question and trying to draw it out, it appeared to be flawed because the conclusion that having higher numbers of male ducks relative to female ducks (MMD) means that there are more older male ducks (OMD) seems to reverse and change the premise that in populations of more older ducks (OD), there tends to be a higher proportion of males (MMD). And converses are not valid, right? Let alone those that change the terms of the initial premise... Another question that I had on this is that I am not sure to what degree this element actually matters — because even though I thought the argument was flawed, I still had to accept it to be "valid" for the purposes of the Must Be True question and to infer based on its conclusion, right? In Must Be True cases, do I need to be checking the validity of the argument so carefully? It didn't impact me getting the answer right or wrong because I had to accept the passage anyway and infer from it... plus it took up a lot of time. Thanks so much!