Question: what is the least common factor of 4 and 7?
Answer: 7: 7,14,21,28,35,42,49,56,63,70,77... Then you find the first number which 4 and 7 have in common. 4 and 7 have 28 and 56 in common BUT the LCM would be 28 since that's the LEAST common, or the smallest number that they would have in common.