// Numbas version: finer_feedback_settings {"name": "NB4 - HCF", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "NB4 - HCF", "tags": [], "metadata": {"description": "Calculating the LCM and HCF of numbers by using prime factorisation.", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "

By considering the prime factorisation of $\\var{x}$ and $\\var{y}$, or otherwise, find the highest common factor (HCF) of $\\var{x}$ and $\\var{y}$.

", "advice": "

We can write $\\var{x}$ and $\\var{y}$ as a product of prime factors as follows:

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$\\var{x}=\\var{show_factors(x)}$

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$\\var{y}=\\var{show_factors(y)}$

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For HCF of $\\var{x}$ and $\\var{y}$ we need to multiply each prime factor the least number of times it occurs in either $\\var{x}$ or $\\var{y}$

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i.e. HCF$(x,y) = \\var{show_factors(hcf_xy)}=\\var{hcf_xy}$

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Use this link to find some resources which will help you revise this topic.

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