document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=731105>Question 731105</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A bag contains 12 red and 8 blue marbles.  If you randomly select 2 marbles, what is the probability that they are the same color? \r<BR>\n" );
document.write( "\n" );
document.write( "I feel like this is an nPr or a nCr, but I am unsure.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #853026 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13258)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=853026\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "It's an nCr problem and not an nPr problem, because order does not matter.<br><BR>\n" );
document.write( "The total number of possible outcomes is choosing 2 of the 20 marbles: 20C2.<br><BR>\n" );
document.write( "The favorable outcomes are choosing 2 of the 12 red marbles AND 0 of the 8 blue marbles OR 2 of the blue marbles AND 0 of the 12 red marbles. Note that the \"AND\"s indicate multiplication and the \"OR\"s indicate addition:<br><BR>\n" );
document.write( "(12C2 * 8C0) + (8C2 * 12C0).<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28C%2812%2C2%29%2AC%288%2C0%29%2BC%288%2C2%29%2AC%2812%2C0%29%29%2FC%2820%2C2%29 ALIGN=MIDDLE  ALT=\"%28C%2812%2C2%29%2AC%288%2C0%29%2BC%288%2C2%29%2AC%2812%2C0%29%29%2FC%2820%2C2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2866%2A1%2B28%2A1%29%2F190=94%2F190=47%2F95 ALIGN=MIDDLE  ALT=\"%2866%2A1%2B28%2A1%29%2F190=94%2F190=47%2F95\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "Or you can get the answer without using nCr, by looking at the probabilities of picking one marble at a time, as the other tutor does.<br><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );