Answer: The required probability is 65.26%.
Step-by-step explanation: Given that two students form a group of eight boys and 12 girls are sent to represent the school in a parade.
We are to find the probability that the students chosen are not both girls, if the two students are chosen at random.
Total number of students in the group = 8 + 12 = 20.
Let S denote the sample space for the experiment of selecting two students and A denote the event that both the students are not girls.
Then,

Therefore, the probability of event A is given by

Thus, the required probability is 65.26%.