Answer :
in a class of 12 boys and 9 girls, the teacher selects three students at random to write problems on the board then the probability that all the students selected are boys is 0.165
given that a class consists of 12 boys and 9 girls. The teacher picks three students to present their work to the rest of the class and says that the three students are being selected at random
Here selecting any 3 students from the group of total 21 students is combination because order does not matter.
Total no of ways of selecting any 3 from total 21 = 21C3 = 1330
No of ways of selecting only 3 boys = No of ways of selecting random 3 boys from total 12 boys
= 12C3 =220
the probability be that all three students
selected are boys=220/1330 = 0.165
Hence , the probability that all the students selected are boys is 0.165
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