Answer:

Suppose a bag contains 3 red counters and 2 black counters. A counter is removed at random and then another one is removed at random. The probability that the second counter is red depends on (is conditional on) the colour of the first counter removed.The conditional probability that the second counter is red, given that the first counter is black is 3/4.

Conditional probability is the probability of some event A, given the occurrence of some other event B. Conditional probability is written P(A|B), and is read the probability of A, given B.