🎓 Deeper Dive — Adults

HCF (or GCD) is the largest integer dividing both. LCM is the smallest integer divisible by both. Useful identity: LCM(a,b) × HCF(a,b) = a × b.

Compute via prime factorisation: take min powers for HCF, max powers for LCM. Example: 12 = 2²·3, 18 = 2·3² → HCF = 2·3 = 6, LCM = 2²·3² = 36.

Euclid's algorithm: HCF(a,b) = HCF(b, a mod b). Used in cryptography and computer science.