Question

A bag has 5 red marbles, 6 blue marbles and 4 black marbles. What is the probability of picking a
black marble, replacing it, and then picking a black marble?

Answer 1

The probability that you choose a black marble is:

# of black marbles / total # of marble >>> 4/(5 + 6 + 4) = 4/15

Then, if you replace that marble, you put it back, so that there is no difference in the pile. The probability that you pick another black marble is the same: 4/15.

Multiply these two fractions together and you get:

(4/15) * (4/15) = 16/225.

The answer is 16/225.

Answer 2

A bag has 5 red marbles, 6 blue marbles and 4 black marbles

so total no. of marbles = 5 + 6 + 4 = 15

now probability of picking a black marble = 4/15

after replacement again probability of picking black marble is 4/15

it is given that black marble is picked two times

so probability of picking black marble two times or picking , replacing , and then picking is 4/15*4/15 = 16/225