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anonymous

  • 5 years ago

two number cubes are rolled. what is the probability that the sum will be even ?

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  1. sandra
    • 5 years ago
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    ok so the probability of something occurring is always (#cases where event occurs)/(#total number of possible cases)

  2. sandra
    • 5 years ago
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    so in the case of dice, there are 36 possible roles of the dice (6 possiblities for the first , and 6 possibilities for the second - so 6 x 6)

  3. anonymous
    • 5 years ago
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    alright. which is 36?

  4. sandra
    • 5 years ago
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    so by brute force, you can actually list all of the combinations, and then count the number that are even: Dice 1, Dice 2, Sum, Odd/even 1. 1, 1, 1+1=2, even 2. 1, 2, 1+2=3, odd 3. 1, 3, 1+3=4, even and so on... until you've listed all 36

  5. anonymous
    • 5 years ago
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    wait (6) (6)^2?

  6. sandra
    • 5 years ago
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    and then the answer is the number of even possibilities/36

  7. sandra
    • 5 years ago
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    you were correct - there are 36 possible combinations when you roll a dice

  8. anonymous
    • 5 years ago
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    so 36 possible even number? 6/36?

  9. sandra
    • 5 years ago
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    1 and 1, 1 and 2, 1 and 3, and so on. But since you know that the number of possiblities for each individual dice is 6, the total number of possibilities when you roll two of them is 6 x 6 = 36

  10. sandra
    • 5 years ago
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    now you want to know, out of those 36 possible combinations, how many add up to be an even number?

  11. sandra
    • 5 years ago
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    you can brute force the solution by listing them all, and their sums, and know that the probability is #evensums/36

  12. anonymous
    • 5 years ago
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    yea. probability some will be even

  13. anonymous
    • 5 years ago
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    (6/36) (6/36)

  14. sandra
    • 5 years ago
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    hmm, the question said "sum", not "some"

  15. anonymous
    • 5 years ago
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    sum****** my bad lol

  16. sandra
    • 5 years ago
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    so a sum is even when you add an even and an even, OR an odd and an odd

  17. anonymous
    • 5 years ago
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    when you add two even numbers together you get an even sum and when you add two odd nubers together you gat an even sum otherwise it is odd.

  18. sandra
    • 5 years ago
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    great minds think alike =)

  19. sandra
    • 5 years ago
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    so what's the probability that both are even numbers? Well, since there's 3/6 chance for the first dice being even, and 3/6 chance the second dice is even, there's a 3/6 * 3/6 = 1/4 chance of both being even

  20. sandra
    • 5 years ago
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    what's the probability of them both being odd?

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