Algebra 9
3 marks · NormalA student claims that all prime numbers are odd. Explain, giving a counter-example, whether this claim is true or false.
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Must show: Reference to 2 being prime and even
Also accept: The number 2 is a prime number and it is even.; Example: 2 is an even prime.
Common mistakes: Giving 1 as a prime number
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States clearly that the claim is false.
B2 · 1 mark · Provides a valid counter-example (2 is a prime number and even).
B3 · 1 mark · Clearly explains why the counter-example disproves the claim.
Worked solution
The claim is false.
2 is a prime number but it is even, not odd.
Since 2 is the only even prime, not all primes are odd. Therefore, providing the example of 2 disproves the claim.