bonanova Posted February 22, 2009 Report Share Posted February 22, 2009 This question is adapted from a [u.S.] national math competition question at the High School level. A fair coin has the letters a and B on its two sides. A fair die has two sides labeled D, two labeled e and two labeled i. Another fair coin has the letters n and r on its two sides. The coins and die are each tossed three times. Find the probability that the nine letters so obtained can be used to spell BrainDen. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted February 22, 2009 Report Share Posted February 22, 2009 (edited) (3/4)*(2/9)*(3/8)= 18/288 = 6,25% Edited February 22, 2009 by TrueMaja Quote Link to comment Share on other sites More sharing options...
0 Guest Posted February 22, 2009 Report Share Posted February 22, 2009 (edited) This question is adapted from a [u.S.] national math competition question at the High School level. A fair coin has the letters a and B on its two sides. A fair die has two sides labeled D, two labeled e and two labeled i. Another fair coin has the letters n and r on its two sides. The coins and die are each tossed three times. Find the probability that the nine letters so obtained can be used to spell BrainDen. edit to say: 2/8 was wrong, actually 3/8 get r + 2n: rnn, nrn, nnr. So answer is as previous poster stated. D'oh! 4.16% chance 6/8 possible outcomes of 3 flips of the first coin yeild both an 'a' and a 'B'; 6/27 possible outcomes of 3 rolls of the die yield D, e, and i. 2/8 possible outcomes of 3 flips of coin 2 yield the needed r plus 2 n's. Multiplied out this yeilds 0.04166. I simplified by assuming a 3-sided die, dunno if that messes things up. Edited February 22, 2009 by xucam Quote Link to comment Share on other sites More sharing options...
0 Guest Posted February 22, 2009 Report Share Posted February 22, 2009 1/16 Quote Link to comment Share on other sites More sharing options...
0 Guest Posted February 22, 2009 Report Share Posted February 22, 2009 there is no chance 0/9 Quote Link to comment Share on other sites More sharing options...
0 Guest Posted February 22, 2009 Report Share Posted February 22, 2009 there is no chance 0/9 never mind mis read Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted February 23, 2009 Author Report Share Posted February 23, 2009 TrueMaja and SCSW have it. xucam too, maybe - I'm not sure he agrees with TM or not. His edit may have gotten mangled. Multiply three different probabilities. Quote Link to comment Share on other sites More sharing options...
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bonanova
This question is adapted from a [u.S.] national math competition question at the High School level.
A fair coin has the letters a and B on its two sides.
A fair die has two sides labeled D, two labeled e and two labeled i.
Another fair coin has the letters n and r on its two sides.
The coins and die are each tossed three times.
Find the probability that the nine letters so obtained can be used to spell BrainDen.
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