In your exam you may be asked to find the Lowest Common Multiple of two numbers. The easiest way to do this is to follow this process. First of all find the highest common factor of both numbers. Second multiply the two numbers you were given in the question. Third, divide your answer by the highest common factor and you will have found the lowest common multiple. For example find the Lowest Common Multiple of 16 and 40. First find the HCF of 16 and 40 which is 8. Now multiply 16 and 40 which is 640. Now divide 640 by 8 to give you the LCM which is 80.