There are 18 balls in a jar. You take out 3 black balls without putting them back inside, and now the probability of pulling out a black ball is 1/3. How many blue balls were there in the beginning?
Answers: A) 12. B) 9. C) 8. D) 7. E) 6.
8 = 3 blue balls + 15 / 3   Answer: 8.
<result>C</result>
There are 18 balls in a jar. You take out 3 black balls without putting them back inside, and now the probability of pulling out a black ball is 1/3. How many blue balls were there in the beginning?