# Which one of the following CANNOT be true?

Audrey-Swope on August 14, 2019

True vs. False

Is there any video or way to help with true and false questions since the only thing I was given was the ying and yang? I'm confused on these types of questions and would like more instruction on them. Thanks.

Replies

Skylar on July 26, 2020

@Audrey-Swope, I'm happy to help explain the concept!

This question asks us to identify the answer choice that CANNOT be true. This means...
- The correct answer (1 answer choice): cannot be true = must be false
- The incorrect answers (4 answer choices): could be true = not necessarily false
In other words, we would test each answer choice to see if it's possible. The one answer choice that is impossible cannot be true and is therefore correct.

You may find it helpful to memorize the following:
- Cannot be false/must be true are logical equals and are the opposites of could be false/not necessarily true, which are logical equals.
- Not necessarily false/could be true are logical equals are are the opposites of must be false/cannot be true, which are logical equals.

When you encounter a question stem that uses the word false, it may be helpful to begin by translating it into its logical equivalent that uses the word true. Then you can identify what criteria would be correct and what criteria would be incorrect, as we did above. This helps to keep everything straightforward and should become instinctual with practice.

It is also important to understand that if we are told that something could be true, it could also be false. Similarly, if something could be false, it could also be true. However, the two terms are very different when we think about them in terms of "must be true" and "must be false."
- If something "could be true," it is incompatible with something that "must be false." This is because something that must be false cannot be true.
- If something "could be false," it is incompatible with something that "must be true." This is because something that must be true cannot be false.

Does that make sense? Please let us know if you have any other questions!

shannonk68 on July 30, 2020

You may find it helpful to memorize the following:
- Cannot be false/must be true are logical equals and are the opposites of could be false/not necessarily true, which are logical equals.
- Not necessarily false/could be true are logical equals are are the opposites of must be false/cannot be true, which are logical equals.
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This is literally the ying/yang chart repeated.

erica-scott on September 14, 2020

Can someone diagram the answer for this question - I cannot figure it out

jonathanhockman on June 10, 2021

^ same here

jonathanhockman on June 10, 2021

Never mind - i drew it 1-5 descending rather than 5-1 descending .. smh