Probability problem

  1. The question is:
    Two number cubes are rolled--one is red and the other is white. Find the probability that the red cube is a 6 and the sum of the two cubes is 10.

    I said that it is 1/6 for being a 6 and since only a 4 can add up to 10 its 1/6*1/6=1/36. But my teacher said it was wrong. Please help!!!
  2. jcsd
  3. HallsofIvy

    HallsofIvy 41,262
    Staff Emeritus
    Science Advisor

    I must say that I think you are correct and your teacher wrong. Are you sure you two are talking about the same problem? If the problem were just "one cube is 6 and the two sum to 10" then then you could get a 6 on either, and a four on the other: (1/6)(1/6)+ (1/6)(1/6)= 1/18.
  4. Ray Vickson

    Ray Vickson 6,864
    Science Advisor
    Homework Helper

    You are correct; your teacher made a mistake. Your teacher would be correct IF you were not told the color of the "6" die---but you *were* told its color.

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