document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=637500>Question 637500</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A jar contains 24 red and blue marbles. If the probability of selecting a red marble at random is 3/8, then how many red marbles must be added so that the probability of randomly selecting a red marble becomes 1/2 ? \r<BR>\n" );
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document.write( "(1)  3/8  = x/24<BR>\n" );
document.write( "     3[24]= 8x          <BR>\n" );
document.write( "     72   = 8x                          <BR>\n" );
document.write( "      9   =  x\r<BR>\n" );
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document.write( "(2)          9  red marbles<BR>\n" );
document.write( "      24-9 = 15 blue marbles\r<BR>\n" );
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document.write( "(3)   15-9 = 6  more red marbles\r<BR>\n" );
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document.write( "(4)   [9+6]/[24+6]= 15/30 = 1/2\r<BR>\n" );
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document.write( "On step 3 I did not really know what to do so I just guessed and played with <BR>\n" );
document.write( "numbers. I finally arrived at an answer when I subtracted the red marbles from the blue marbles, but I do not understand why this works.Guessing,checking,and luck will take a long time on an exam. How do I solve these type of problems? For example what would I do if I needed to find how many more red marbles are needed to go from a probability of 3/8 to 209/698? Please explain.\r<BR>\n" );
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document.write( "PS: What concepts do I need to review or learn in order to work problems like this or more difficult ones in this area?\r<BR>\n" );
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document.write( "I am sorry this is so long, but I would sincerely appreciate your time and effort with my dilemma.\r<BR>\n" );
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document.write( "   - disgruntled student(Konny)<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #401757 by </B><A HREF=/tutors/aboutme.mpl?userid=DrBeeee><B>DrBeeee(684)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=DrBeeee><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=401757\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> This may help your step 3.<BR>\n" );
document.write( "Let x = number of red marbles to add to get 50%<BR>\n" );
document.write( "You correctly calculated that there are 9 red marbles in the jar. The jar contains a total of 24 marbles is a given.<BR>\n" );
document.write( "You want add x red marbles to the 9 to end up with (9+x) which is 50% or 1/2 the total number, which is now (24 + x) because you also add x to the total.<BR>\n" );
document.write( "This results in the same ratio that you have, except you deduced that x = 6. That is you now have the algebraic equation<BR>\n" );
document.write( "(9+x)/(24+x) = 1/2<BR>\n" );
document.write( "Using cross multiplication we get<BR>\n" );
document.write( "2*(9+x) = (24+x) or<BR>\n" );
document.write( "18 + 2x = 24 + x<BR>\n" );
document.write( "x = 24 - 18<BR>\n" );
document.write( "x = 6<BR>\n" );
document.write( "Answer: You need to add 6 red marbles.<BR>\n" );
document.write( "Now you can rely on your math skill. However, don't toss out your super deductive reasoning.  </SPAN>\n" );
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