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