A bag contains 5 blue marbles, 4 white marbles, and 3 red marbles. If three marbles are randomly selected from the bag, what is the probability that the marbles selected will be of the same color? Express your answer as a common fraction.

In the future I will need a lot of your guy's help to check my answers, as the math competitions are starting soon! and i need to prepare

Also the confirming if I am a robot thing is SUPER annoying. Make it where once you passed the test ONCE, you don't need to do it again if you have an account.

How I did it:

5 + 4 + 3 = 12 total number of marbles

that means 12 choose 3 = 220 ways to choose 3 marbles

Now the question asks how many ways will the marbles be the same color

So for red

there is only 1 way

For White,

there is 4 ways of choosing 3 out of 4

And for blue

there is 10 ways of choosing 3 out of 5

So is 1 + 4 + 10 = 15 ways you can pick three marbles of the same color

So 15/220 = 3/44

CalculatorUser Sep 15, 2019

edited by
CalculatorUser
Sep 15, 2019

edited by CalculatorUser Sep 15, 2019

edited by CalculatorUser Sep 15, 2019

edited by CalculatorUser Sep 15, 2019

edited by CalculatorUser Sep 15, 2019

#1**+2 **

Not great at probability, but we could either draw 3 red marbles, 3 blue marbles or 3 white marbles

P(red) = (3/12) (2/11) (1/10) = 6 / 1320

P( blue) = (5/12) (4/11) (3/10) = 60/1320

P(white) = (4/12) (3/11)(2/10) = 24 / 1320

So.....the total probability = [ 6 + 60 + 24 ] /1320 = 90 / 1320 = 9 /132 = 3 / 44

Good job, CU [ At least we got the same answer !!! ]

CPhill Sep 15, 2019