Bunuel wrote:
shrive555 wrote:
ooo... i'm so dumb !! the denominator with 7C3. choosing 3 out of 7 but whats wrong with the 2nd method ?
I'm not sure what are doing in your second approach but using probability you can solve:5/7*4/6*3/5=2/7.
Bunuel how about reverse probability? this is what i tried and ended up with the wrong answer:\( 1-\frac{2}{7}*\frac{1}{6}*1+\frac{2}{7}*\frac{5}{6}*\frac{4}{5} =1-\frac{5}{21} \)
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