A question about "some" and "most" relationship

linfan.zha

Most A are C; Most B are C, can we make the link that "some A are B"?

stepharizona

No you can't. Some statements are reversible but Most statements are reversed to some statements.

So some Cs are As and some Bs are Cs but you can't go

B some C some A
To be B some A or A some B.

You can only link 2 mosts when the left side is the same

so

A--m-->B
A--m-->C
--------------------
B-- s --C

Would be a valid conclusion.

MrSamIam

+1 @stepharizona

To solidify it, here's an example:
Most A are C. So, if we have 10 As, lets say that 6 of them (most) are C (so we have 6 AC, and 4 separate As).
Most B are C. So, if we have 10 Bs, lets say that 6 of them (most) are C (so we have 6 BC, and 4 separate Bs).
Can we come up with a situation where NO As are Bs (thus disproving the A Some B statement)?
Sure we can: Look above. Did we ever link an A to a B? Nope, not a single time.

To piggy back on Stephanie's statement (I think that's your name, @stepharizona forgive me if it's not!):

A most B (so, we have 6 AB and 4 separate Bs)
A most C (so, we have 6 AC, and 4 separate Cs)

But wait a minute, if there are only 10 "A" on this planet, we have to at least 2 points of intersection between B and C. To meet the minimum requirement of the two statements above, it would look like this:

AB
AB
AB
AB
ABC
ABC
AC
AC
AC
AC

There's a lesson on Most and Some statements that explains the two terms as they apply to the LSAT incredibly well.

runiggyrun

An example of your premise that Most A are C and most B are C, therefore some A are B would be : Most birds (A) can fly (C). Most airplanes (B) can fly (C). Some birds are airplanes (some A are . You can see that it doesn't work.
The relationship, as explained by @stepharizona and @MrSamlam only works if you are talking about two subsets of the same world. (like Most A are B and Most A are C, then some B are C) Most birds can fly. Most birds build nests. Some things that can fly build nests.