Syllogisms & Formal Logic

"All squares are rectangles" — knowing this, Prisha thinks it can also be flipped around to say: "All rectangles are squares." Her brother says flipping it is wrong here. Who is right?

"If it rained last night, the ground is wet. This morning the ground is wet. So it must have rained." Aarav thinks this reasoning is solid. His sister says the ground could be wet for other reasons. Who is right?

"All dogs are animals. All cats are animals. Therefore all dogs are cats." — hearing this, Karan thinks this reasoning is correct, since both starting sentences are true. His sister says the conclusion is wrong even though both sentences are true. Who is right?

"Some furniture is made of wood. Some wooden things are trees. Therefore some furniture is a tree." — Nisha thinks this reasoning is correct, since both sentences sound right. Her friend says the whole PATTERN of this reasoning is broken. Who is right?

A shop sign reads: "Some of our sweets are sugar-free." Ishani concludes from this that "some of the sweets are not sugar-free." Her friend says that does not necessarily follow. Who is right?

"No fish are mammals. All whales are mammals. Therefore no whales are fish." — Abhay thinks this reasoning is just as broken as the earlier "some A, some B" reasoning. His sister says this particular reasoning is actually valid. Who is right?