Ethnics final part 1

Either January or February was the coldest month this year. January was clearly not the coldest month. Therefore, February was the coldest month this year.

Either January or February was the coldest month this year. January was clearly not the coldest month. Therefore, February was the coldest month this year.

Either June or July was the hottest month this year. July was the hottest, so it cannot be June.

Invalid

If UFOs exist, then there is life on other planets. UFOs do not exist. Thus it is not the case that there is life on other planets.

Invalid

If the prosecuting attorney's claims are correct, then the defendant is guilty. The defendant is guilty. Therefore, the prosecuting attorney's claims are correct.

Invalid

If the prosecuting attorney's claims are correct, then the defendant is guilty. The defendant is not guilty. Therefore, the prosecuting attorney's claims are correct.

Invalid

If your motorcycle is burning oil, then it is wasting energy. If your motorcycle is burning oil, then it is also wasting your money. So if your motorcycle is wasting energy, then it is also wasting your money.

Invalid

If bananas are fruit, then bananas are plants. If bananas are plants, then bananas use photosynthesis. So, if bananas are fruit, then bananas use photosynthesis.

Valid; hypothetical syllogism

Descartes is French. If Descartes if French, then he is a philosopher. So Descartes must be a philosopher.

Valid; modus ponens

If the prosecuting attorney's claims are correct, then the defendant is guilty. The defendant is not guilty. Therefore, the prosecuting attorney's claims are not correct.

Valid; modus tollens

If you take 1000 mg of vitamin C every day, then you will not get a cold. You get a cold. Thus, you did not take 1000 mg of vitamin C every day.

Valid; modus tollens