Question

A bag contains 6 blue marbles, 10 red marbles, and 9 green marbles. If two marbles are drawn at random without replacement, what is the probability that two red marbles are drawn?

Answer 1

So since there are 6 blue marbles, 10 red marbles, and 9 green marbles, that means that there are 25 marbles in total. This means the chance of pulling ONE red marble is 10/25 which simplifies to 2/5. If you want to pull 2 red marbles, you'd multiply the chance of pulling one marble to the chance of pulling one marble. (2/5 times 2/5)
You'd get 4/10. Which is a 40% percent chance.
(not completely sure about this one..)

Answer 2

6 blue, 10 red, 9 green...for a total of 25 marbles

P(1st one drawn is red) = 10/25 reduces to 2/5
without replacement
P(2nd one drawn is red) = 9/24 reduces to 3/8

P(both events happening) = 2/5 * 3/8 = 6/40 reduces to 3/20 <=