Jennifer offers some good advice in her newsletter, but she also oversimplifies some things. For example, Jenn says, "Remember that and = multiply, or = add". Language is used in many different ways, and it's easy to think of ways in which Jennifer's rule is just plain wrong. For example, if I take 4 eggs in one basket AND 6 eggs in another basket and combine them, how many eggs do I have? Obviously the answer is 10. But notice that this sentence uses AND and does not use OR, and yet the proper arithmetic is to ADD, not MULTIPLY. So be careful with generalizations like the ones suggested.

Furthermore, such "rules" are frequently misapplied by those who lack understanding. For example, in general if A and B are events, then it's NOT true that the probability that A and B occur can be obtaining by multiplying P(A) times P(B). This is true ONLY when the events are independent (see Section 5.6). So just blindly plodding along and multiplying every time you see an "AND" in a problem isn't going to get you very far.

No matter how much you try to tighten up such rules, the rules are no substitute for thought and a little understanding. Don't be afraid to think. A little thinking will take you a long way in Chapter 5.