You just learned how to read tables. It might not seem like it at first glance, but tables use addition, subtraction, and number families. Let's look at the table we just saw about the left-handed and right-handed boys and girls in a class. This time, though, let's add one new row and one new column.
The new column we added tells us the total number of boys and girls in the class. The new row gives the total number of left-handed students and right-handed students. How did we come up with those numbers? You guessed it. We added the rows and columns. For example, we know there are three left-handed boys and two left-handed girls. So by adding three and two, we know there are five left-handed students in all.
We can also use subtraction to help us complete the table. Let's say you wanted to know how many right-handed boys are in the class, but-oops!-you spilled ink on your paper and blocked out part of the table. Well, that's okay. You can use the other information in the row to find the answer. The table tells you that there are 13 boys total in the class. It also tells you that three of the boys are left-handed. So just subtract 3 from 13, and you can figure out that 10 of the boys are right-handed.
