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2. Robot combinations

Let's review the multiplication principle which allows us to quickly count the number of possible robots.

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Video transcript

- In the previous video and exercise, we saw how a table is a great way to keep track of a lot of different kinds of robots, where each robot is made up of one head and one body. Let's call each of those different robots a combination. You experience combinations all the time. For instance, when you wake up in the morning and you pick out a top and some bottoms to wear, that's a combination. Notice that since each cell in the table corresponds to a different combination, we just need to count the number of cells, but we don't have to count one by one. That's because the number of cells in a table is just the number of rows times the number of columns. So, with two heads and three bodies, we have two times three or six different combinations. And, with three heads and four bodies, we have three times four or 12 different combinations. The next exercise will give you a chance to practice with other combinations.