ITPEC FE Subject B October 2025 Question 5

Math & Numbers — Filling in a prime-number printing procedure by identifying where to set isPrime ← false and where to increment the found-primes counter.

The program uses a while (count ≤ N) loop to find the first N primes. For each candidate number, it checks divisibility by all integers from 2 up to √number.

• •Blank A (inside if (number mod i = 0)): When a divisor is found, the number is not prime, so we set isPrime ← false, then exit the for loop.
• •Blank B (inside if (isPrime = true)): The number passed all checks — it is prime, so we increment count ← count + 1 to track how many primes have been found.

Answer: c) — A: isPrime ← false, B: count ← count + 1

Why not others:
- a) count ← count + 1 in A would increment the counter when a divisor is found — the opposite of correct
- b) count ← count + i in A is nonsensical — adds the loop variable to the counter
- d) count ← count + i in B would add arbitrary values instead of incrementing by 1

Key rule: In a prime-checking loop, finding a divisor means not prime → set a flag. Incrementing the prime counter happens only after confirming primality.

AI-generated — may contain errors