find the probability? please show me how to do it?

A pair of dice is rolled. What is the probability of getting a sum of 2?

In a class of 30 students, there are 17 girls and 13 boys. Five are A students, and three of these students are girls. If a student is chosen at random, what is the probability of choosing a girl or an A student?

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  • 1 decade ago
    Favorite Answer

    each die has 6 ways it can land

    only one of them is a 1

    so chance of one die getting 1 is 1/6

    same with the other one

    So the odds of rolling "snake eyes" is 1 in 36

    chance of being a girl is 17 out of 30 or 17/30

    chance of being an A student is 5 out of 30 (5/30) or 1/6

  • Anonymous
    1 decade ago

    What is probability?

    Let P = the word probability here. Okay?

    P = number of times an event can happen divided by the total number of possible outcomes

    A dice has 6 sides.

    How many times does 2 appear in 1, 2, 3, 4, 5 , 6?

    How many times can we make the sum of 2 from the list?

    Only once, right?

    We have:

    P(sum of 2) = 2/6 sides

    P(sum of 2) = 1/3

    ++++++++++++++++++++++++

    For question 2, we can use this formula:

    P(A or B) = P(A) + P(B) - P(A and B)

    Think you can take it from here?

    Guido

  • 1 decade ago

    Firt question) It depends if you can tell the difference between the two dice.

    Is it a red and a blue die or are they the same.

    Like rolling a one and a six is the same as rolling a six and a one if they are the same dice.

    So the question alone isn't specific enough for me to answer.

    You should tell your teacher what I told you just to tick him off.

  • Anonymous
    4 years ago

    7 a. The risk of having one question precise is a million/4. The risk of having one question incorrect is 3/4. subsequently the opportunities are against you. In a pool of one hundred questions, you like 30 questions to be ultimate suited. in case you have no longer carried out nCr in arithmetic this could be no longer effortless to describe. in case you have carried out tree diagrams in college you could understand this. There are 2 opportunities, getting the question precise and getting the question incorrect. on account which you desire to get 30 questions precise you ought to do ( a million/4)^30, on account which you ought to get the question precise 30 situations, yet this leaves the latter helf with the 70 questions you acquire incorrect: (3/4)^70. Now all of us be attentive to that to calculate this risk, we ought to contain (a million/4)^30 X( 3/4)^70.although, right that's what gets problematic. In a pool of one hundred questions, you like 30 questions to be ultimate suited. In mathematical words we are able to write this as 100C30 ( attempt and style that into your medical calulator! The form of combos possible while figuring out on 30 in a pool of one hundred is huge and just about is the form of combos to get precise interior the examination. THis ought to be elevated onto what we've. in fact this: 100C30X(a million/4)^30X(3/4)^70 = 0.0458 b) with what replaced into pronounced in the previous, we are assuming that we've become 30 and extra questions ultimate suited. there's a speedy way, yet so as to know it properly we are going to ought to do it the long-winded way. To calculate the respond takes utter precision and staying power, by way of fact we are going to ought to calculate the probabilities of having 29,28,27... all a thank you to 0 questions precise and then minus the respond off from a million. i won't be able to do the entire calculation yet i visit get the answer to an desirable diploma of accuracy. answer approximately equals...0.14 wish this explains!

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  • 1 decade ago

    well there is only possibility.....

    1 and 1... or 1 favourable outcome

    the total number of possibilties is....

    1,1 1,2 1,3 1,4 1,5 1,6

    2,1 2,2 2,3 2,4 2,5 2,6

    3,1 3,2 3,3 3,4 3,5 3,6

    4,1 4,2 4,3 4,4 4,5 4,6

    5,1 5,2 5,3 5,4 5,5 5,6

    6,1 6,2 6,3 6,4 6,5 6,6

    total no of outcomes possible: 36

    thus probability = 1out of 36

    sorry cant help you with the second Qn

  • 1 decade ago

    1/36

    19/30

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