CIE A Level Maths: Probability & Statistics 1复习笔记2.3.4 Probability Formulae

In the fictional World Stare Out Championships players compete by staring at each other with the player blinking first losing.  A match cannot be drawn.

During each day of the championships three matches are scheduled to take place but if the first two matches both take more than an hour each, then the third match cannot take place that day.

A statistician notices from past fictional championship records that the probability of the first match taking longer than an hour is 0.15 and that the probability of only two matches taking place on any day is 0.06.  They also notice that the probability that at least one of the first two matches takes longer than an hour is 0.32.

Find the probability that

• If in any doubt always start with a diagram
  • a Venn diagram can be used for most problems
  • a two-way table can be easier to read if it’s possible to construct one
  • a tree diagram is useful if you are looking at an event that follows another
• Remember that all probability formulae are given in the formulae booklet but not necessarily in the most user-friendly way; a quick look could just be enough to jog your memory though!