A bag contains four red marbles, eight green marbles, three blue marbles, and nine yellow marbles. If Lisa draws a random marble from the bag, what is the probability that it will be a red, green, or blue marble?

Question

anonymous · Answer

red = 4/20 2/10               1/5       <--- i reduced them 
green= 8/16  4/8 2/4        1/2       <----
blue = 3/21          1/7    <----

anonymous · Answer

1/8?

anonymous · Answer

I mean for like the total? alll of them together probability

anonymous · Answer

4/24   2/12 1/8  so yeah 1/8 is correct!

anonymous · Answer

can I ask u another?

anonymous · Answer

sure why not

anonymous · Answer

Holly is taking a multiple choice reading test. She has decided to guess on questions 3 and 7. On each question, there are four worded choices plus an "all of these" choice and a "none of these" choice. What is the probability that she answers question 3 correctly and question 7 incorrectly?

anonymous · Answer

When there are 6 choices, and 5 of them are INcorrect
P(INcorrect) on each question if 5/6.

To get the overall probability for two questions you multiply
the individual probabilities.

5/6 * 5/6 = 25/36 chance of getting both wrong.

To check you can compute the remaining cases:

Both right: 1/6 * 1/6 = 1/36
first right, second wrong: 1/6 * 5/6 = 5/36
same for other way around = 5/36

Total = 36/36 = 1 as it should be.

anonymous · Answer

thanks! I was thinking it would be 5/36

anonymous · Answer

u are welcome!