Question

A bag contains 4 red marbles and 5 blue marbles. If two marbles are chosen at random, one at a time and without replacement, what is the probability of getting two red marbles?

A. 5/18
B. 40/81
C. 16/81
D. 1/6

Answer 1

1/6

Explanation:

for the first marble

it might be red or blue

so P (the first red)=4/9

then if the first one is red ,

now we have 3 red and 5 blue ,

the second one might be red again or blue

so P(the second red)= 3/8,

ok

now

P(get two red)=P(the first red) X P(the second red)=4/9x3/8=1/6

Answer 2

P(red) 4/9 on the first pull, P(red) 3/8 on the second pull
(4/9)(3/8) = 12/72 = 1/6 Letter D