An amusement park has enough space on its ground to add one more rolle

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I think the question is fine.

Premise: Studies show that only young children are fans of the television series,

Conclusion: the amusement park will be better served by building the roller coaster based on the action film.

There is a gap here. The premise tells us that only young children are fans of tv series, not adults. We are concluding from that that the park will be better served by basing it on the movie. Why? Why is it not ok to cater to young children through the roller coaster? The roller coaster could very well cater to young children successfully. What is the problem?

The assumption here is that the roller coaster will be predominantly considered by adults, not young children. Only then does it make sense that the park will be better served by not basing it on the tv series. 

Assumption: Most of the people who will consider riding on the new roller coaster are not young children.
"Most" means the "key demography" is not young children, that's all. 

Something that supports the assumption: Most young children are not tall enough to ride on roller coasters
(and hence they will not consider riding it)

­Hi  [url=https://gmatclub.com:443/forum/memberlist.php?mode=viewprofile&un=KarishmaB]KarishmaB

Please help me out here.
I still don't see why ''MOST'' is REQUIRED, and without it the argument won't work. Below is my reasoning:

Premise: Studies show that ONLY young children are fans of the television series,
Conclusion: the amusement park will be better served by building the roller coaster based on the action film.

Television series has ONLY young children FANS = 10 million
Popular action film = Both adults and children are Fans(Young children = 10 million, Adults = 9 million)
If that is the case then arguments still works fine, right?  Negating the assumption doesn't even weaken the argument, because amusement park is still ''better served'' with more audience.

I have never seen a necessary assumption using such strong language.
Rather a necessary assumption will say: ''some adullts will consider going to the ride''. If we negate this statement, argument won't work.­

­Hey Ashutosh, the question seems fine. No need to retire it. I think you missed a beat here; I'll try to explain it better:

In the argument provided, the conclusion is drawn based on the premise that "only young children are fans of the television series." The argument then suggests that, due to this premise, the amusement park would be better served by building the roller coaster based on the action film.

Now, the assumption here is not about whether some adults will consider going on the ride. Rather, it's about the primary demographic that the amusement park should target with its new roller coaster. The assumption is necessary because it bridges the gap between the premise and the conclusion. Without assuming that the target demographic for the new roller coaster primarily consists of individuals other than young children, the conclusion that the park should build the roller coaster based on the action film doesn't logically follow.

Regarding your point about the term "most" being ambiguous, it's important to note that in logical reasoning, "most" typically refers to a majority or a significant portion. Even if we interpret "most" as 51%, the assumption still holds because it establishes that the primary audience for the roller coaster would likely be individuals other than young children.

In essence, the assumption ensures that the argument's conclusion logically follows from the given premises. It's not about whether some adults may consider going on the ride, but rather about the overarching demographic that the roller coaster should cater to.

Hope it is clear.­

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Think about the context of the argument. 
Theme 1 is liked by kids alone. Theme 2 is liked by adults. When will a park be better served? When the majority that is going to consider riding it, likes the theme.  Note that in either case, in an amusement park, a ride could be taken by both adults and kids. It should appeal to the "key demography". Some adults will take kids rides too and some kids will take adults rides too (as long as they are allowed etc)

If kids will consider riding it mostly (80%) and some adults (say 20%) will consider riding it, theme 1 is better.
If adults will consider riding it mostly (80%) and some kids (say 20%) will consider riding it, theme 2 is better. 

Hence when we say that theme 2 is better suited, it must mean that most who will consider riding it are adults.
Do not think about strong language. It depends on what the argument is and the context.