hcf lcm

$$ LCM (p,q,r)=\frac {p.q.r. HCF(p,q,r)} {HCF(p,q). HCF(q,r). HCF(p,r)}

$$

$$ HCF (p, q, r)=\frac {p.q.r. LCM (p,q,r)} {LCM (p,q). LCM(q,r). LCM(p,r)} $$