Thread: Probability Test

Gah i posted 2 questions about my test earlier, cud u pls check it

Hello,

Questions 1, 2 and 3 are ok.

Question 4 :

a.) The first marble picked is black and the second is red: 5/36

I don't see any black marble :/

b.) Obtaining 2 white marbles: 1/16

Ok.

Find One Lol

Good job !

booo

Yes ^^

Unless I made mistakes too, but all the reasoning is correct !

haha i doubt two people can make the exact same mistake

So far #1 and #2 are correct, but #3 has an error...

3.) A red and a black die labelled 1 - 6 are thrown simultaneously, find the probability of:

a.) A number less than 5 on the red die: 2/3
b.) A number less than 5 on the red die but a totla of 10 altogether: 1/36
c.) Both die adding to 10: 1/12

a) is correct

given that, b) should be equal to

c) is correct, three possibilities out of thirty-six

4.) There is 3 white marbles, 4 blue marbles and 5 red marbles in a bag. Find the probabilty of if marbles are picked WITH REPLACEMENT:

a.) The first marble picked is black and the second is red: 5/36
b.) Obtaining 2 white marbles: 1/16

a) 0, there are no black marbles
b) , Remember, the white marble is replaced by another white marble.

#5, #6 and #7 are all correct

Note: Best way to solve #7 is by using a Venn diagram

Originally Posted by colby2152

a) 0, there are no black marbles

He said it was blue

b) , Remember, the white marble is replaced by another white marble.

The probability to get a white marble is 3/12=1/4
Since there is replacement, the probability to get 2 marbles will be the product of the probabilities of getting 1 marble, that is to say 1/4²=1/16, isn't it ?
Actually, 9/144 is 1/16...

Originally Posted by colby2152

given that, b) should be equal to

The thing is that the red dice has to be < 5, so 1 2 3 or 4.
Since the total has to be 10, the only possibility is that the red dice is 4 and the blue dice is 6 -> 1/36

Originally Posted by Moo

The probability to get a white marble is 3/12=1/4
Since there is replacement, the probability to get 2 marbles will be the product of the probabilities of getting 1 marble, that is to say 1/4²=1/16, isn't it ?
Actually, 9/144 is 1/16...

Yep,

Originally Posted by Moo

The thing is that the red dice has to be < 5, so 1 2 3 or 4.
Since the total has to be 10, the only possibility is that the red dice is 4 and the blue dice is 6 -> 1/36

Both adding to 10 is the event of a 6 on one die and a 4 on another. This probability is 1/36. I read the question wrong.