+0

i don't get probability

0
44
1

There are 4 white marbles, 6 red marbles, and 2blue marbles. Once a marble is selected, it is not replaced. Find the probability of selecting 2 blue marbles.

Feb 11, 2021

#1
+112552
+1

Initially there are 12 marbles.  and 2 of those are blue.

so the chance of choosing a blue one is  2/12

That marble is not put back so there are now 11 marbles and only 1 of them is blue.  So the chance of choosing a blue one this time will be 1/11

The chance of getting 2 blue marbles is     $$\frac{2}{12}\times \frac{1}{11}=\frac{1}{66}$$

Feb 11, 2021