Easy -2.0 This is a trivial 2-mark question requiring only checking divisibility by primes up to √23 ≈ 4.8 (i.e., testing 2 and 3). It's pure recall of the primality test definition with minimal computation, significantly easier than typical A-level questions which involve multi-step problem-solving.
Question 5:
5 | Begins checking for factors to start
proof by exhaustion or makes a
statement about numbers which
don’t need to be checked | AO3.1a | M1 | 234.8so only need to check 2
and 3
23 is odd so no need to check 2.
23 is not a multiple of 3
23 is prime.
Completes rigorous argument,
for example:
Only need to check primes less
than 23
23 is not divisible by 2 or 3
therefore 23 is prime
or
checks all possible factors
or
checks more factors than
necessary, but argument must be
complete. | AO2.1 | R1
Total | 2
Q | Marking Instructions | AO | Marks | Typical Solution