The least common multiple is the smallest number that is a multiple of two numbers. "A group of Girl Scouts goes to every 6^th house to sell cookies. Another group goes to every 8^th house. At which house will they first meet?" Answer: the 24^th house. It is the least common multiple of 6 and 8. (6 * 4 = 24 and 8 * 3 = 24).