For Exercise 4.54, see page 195; for 4.55, see page 197; for 4.56, see page 198; for 4.57 and 4.58, see pages 198–199; for 4.59 and 4.60, see page 200; and for 4.61, see page 202.
4.59 What rule did we use?
In Example 4.20, we calculated . What rule did we use for this calculation? Explain why this rule applies in this setting.
4.59
Rule 3. Addition rule for disjoint events. It applies in this setting because a student can’t be in more than one age group, so the four age groups are disjoint.