How to Calculate the Probability of Selecting Two Blue Balls?

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8 balls are in a box. Each ball can be either blue or red. If there are d red balls in the box, calculate the probability p(d) that two randomly selected balls from the ball are both blue. Sketch p(d).

p(d) = \frac{_{8-d}C_{2}*_{d}C_{0}}{_{8}C_{2}} = \frac{_{8-d}C_{2}}{14}

Is this correct? Is there a better way to write it so that I can sketch p(d)?
 
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kasse said:
Is this correct? Is there a better way to write it so that I can sketch p(d)?

Hi kasse! :smile:

P(1st = blue) times P(2nd = blue | 1st = blue) :wink:
 
Of course!
 
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