In essence, in order to solve any HCF and LCM questions, try to find the prime factors of all the numbers involved first. Then you make comparisons and determine accordingly. For HCF, you should consider the lowest powers of all the common primes and multiply together. On the other hand, for LCM, you need to consider the highest powers of all the common primes in addition to the ones that are not common, before multiplying them together. Once you understand this concept, you will no longer have issues with HCF and LCM questions. All the best! :)