document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1191825>Question 1191825</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In a box containing 13 red balls, 9 green balls and 7 yellow balls. Two balls are drawn one by one without replacement, what is the probability that<BR>\n" );
document.write( "(correct your answers to 4 decimal places.)\r<BR>\n" );
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document.write( "(a) both of them are the same color?<BR>\n" );
document.write( "(b) both of them are not green? </SPAN>\n" );
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document.write( "(a) both the same color<br><BR>\n" );
document.write( "This means (1st red AND 2nd red) OR (1st green AND 2nd green) OR (1st yellow AND 2nd yellow)<br><BR>\n" );
document.write( "By basic concepts of probability, \"AND\" translates to a multiplication of the probabilities; \"OR\" translates to an addition of the probabilities.  So<br><BR>\n" );
document.write( "P(both red) = (13/29)(12/28) = 156/812<BR>\n" );
document.write( "P(both green) = (8/29)(7/28) = 56/812<BR>\n" );
document.write( "P(both yellow) = (7/29)(6/28) = 42/812<BR>\n" );
document.write( "P(both the same color) = (156+56+42)/812 = 254/812<br><BR>\n" );
document.write( "(b) both not green<br><BR>\n" );
document.write( "P(both not green) = (20/29)(19/28) = 380/812<br><BR>\n" );
document.write( "You can do the calculations and round to the required number of decimal places.<br><BR>\n" );
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