We’ve covered, in an earlier articles, how to deal with the simplest formal logic statement: If X, then Y. But what happens when our necessary or sufficient factors become more complicated? Let’s look at a couple of examples, using the idea of a vegetable salad. The simplest statement and its contrapositive might look like this:
If the salad has lettuce, then it has tomatoes.
If the salad has no tomatoes, then it has no lettuce.
Now let’s add more vegetables (and more complicated logic):
If the salad has lettuce or spinach, then it has tomatoes and peppers.
Here’s an important idea: when you are forming a contrapositive, you already know that the necessary and sufficient factors are switched around and negated. But now you also have to remember that “and” becomes “or,” and vice versa. So the statement above becomes:
Try this GMAT critical reasoning question for more practice!
