Step-by-step explanation:
I assume it is meant to draw 2 blue balls in a row out of the full pool of balls (no other draws happen before or during this process).
tricky, your teacher.
I think the temptation is to simply say 1/3×1/3 = 1/9.
but is it ?
the probabilty to draw one blue ball out of the complete system (no ball missing) is
x / (6+4+x) = 1/3
x = (6+4+x)/3
3x = 6 + 4 + x = 10 + x
2x = 10
x = 5
so, we have a system of 6 orange, 4 green and 5 blue balls (15 all together) .
the probability at our first pull to draw a blue ball is the indicated 5/15 = 1/3.
but now, for the second ball, we have only 6 orange, 4 green and 4 blue balls in the pool (14 altogether).
and so the probability to draw a blue ball out of this is
4/14 = 2/7.
therefore, the probability to draw 2 blue balls is now the combination
1/3 × 2/7 = 2/21
aha ! so, it is a little bit less than the originally suspected probability of 1/9.
