# Chapter 11 - Counting Methods and Probability Theory - 11.7 Events Involving And; Conditional Probability - Exercise Set 11.7 - Page 747: 49

$\frac{1}{5}$

#### Work Step by Step

The probability of event B, assuming that event A has already occurred, is called the conditional probability of B, given A. This probability is denoted by P(B|A). E: a 3, given that a red disk is selected. A: There are 5 red disks. B: There is only one red disk with a 3, so we can select a disk numbered 3 in only one way given that it is red. P(B|A) = $\frac{1}{5}$

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