# Quantitative Aptitude - HCF & LCM - Formula & Concept Tutorial

**HCF**( Highest Common Factor ) X**LCM**( Least Common Multiple )**of two number**=**Product Of Two Number****HCF**( Highest Common Factor ) or GCD or GCM of fraction =**LCM**( Least Common Multiple ) of fraction =- After getting HCF the remaining no. are co-prime.
- HCF of co-prime number is 1.
- If the sum of two numbers is 100, then 1
^{st}No. is**x**and another no. is**100-x**. - HCF is always a factor of LCM