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[ptraye]

Certain grocery items at the local supermarket are on sale, and all grocery items must be FDA approved.

We can infer that...

1) Most items that are on sale are FDA approved items.

2) Some FDA approved items are on sale.

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2 is correct. but why is 1 wrong.

with #1:
if all items are FDA approved, should the correct way to re-write one be "All items that are on sale are FDA approved items"? also, if all items are FDA approved, can you not logical conclude that most of those items are FDA approved, or must you say that all of them are?

thanks.

[christine.defenbaugh]

Great question, ptraye!

So, first things first:

You are absolutely correct that If ALL A are B, it's legitimate to say that "most A are B" or even that "some A are B". So #1 is not wrong for that reason - there's something else going on!

Notice in your paraphrasing, you said that "all items are FDA approved" - but that's not actually what the information given said. Our information said that all grocery items are FDA approved. That difference matters! There are tons of other items out there (shoes, widgets, umbrellas) that may NOT be FDA approved!

As a result, all we know is that some of the grocery items (which are all FDA approved) are on sale -> so there are some items that are FDA approved-grocery items that are on sale.

We can't say that most items on sale are FDA approved, because we don't know anything about all those possible sale items out in the universe that are NOT grocery items.

If #1 said "most grocery items that are sale are FDA approved" it would be correct! But the fact that it expands to "most ITEMS" makes it unsupportable.

Does that help clear this up a bit?