Multiple choice general knowledge math & puzzles The HCF of 3 & PI is 3 PI 9.42 1 Answer doesn't exist Reveal answer Fill a bubble to check yourself D Correct answer Explanation The Highest Common Factor (HCF) is defined for integers. Since $\pi$ is an irrational number, the concept of HCF between an integer and an irrational number is not defined in standard arithmetic. Therefore, the answer does not exist.