To find the least common multiple for the integers 30 and 42, we start by making a factor tree for each of our integers.
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Notice that our two's match up as factors of each of our integers. The number three also matches up as factors of each of our integers. When finding the least common multiple, we can simply multiply all of our factors together. Since the two's match up and so does the number 3, we only multiply by a two and a three once. Then, we multiply the 5 which does not match up and the 7 which does not match up.