Practice question · Sort into groups
A proposition must have a definite truth value. Sort each sentence.
Groups: Proposition · Not a proposition
- This sentence is false
- 3 > 8
- Is 12 divisible by 5?
- x + 1
- Every even number above 2 is composite
- 17 is prime
Hints
- Being FALSE is fine, a false claim is still a proposition.
- Expressions, questions and self-contradictory sentences have no definite truth value.
Show the answer
Proposition: 17 is prime, Every even number above 2 is composite, 3 > 8
Not a proposition: x + 1, Is 12 divisible by 5?, This sentence is false
Why
'17 is prime' (true), 'every even number above 2 is composite' (true) and '3 > 8' (false) all assert something definite. 'x + 1' names a number instead of claiming anything, a question asserts nothing, and 'this sentence is false' can be neither true nor false, the liar paradox.
Practise Mathematical Statements and Logic
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