document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1190207>Question 1190207</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A full box of ball bearings weighs 21 pounds. The box plus 1/3 of the ball bearings weighs 9 pounds. How much does the box alone weigh?<BR>\n" );
document.write( "A) 4 pounds<BR>\n" );
document.write( "B) 3 pounds<BR>\n" );
document.write( "C) 5 pounds<BR>\n" );
document.write( "D) 6 pounds<BR>\n" );
document.write( "E) 2 pounds\r<BR>\n" );
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document.write( "Let's say there are 90 ball bearings in total. <BR>\n" );
document.write( "I picked something that's a multiple of 3, so that 1/3 of it is some whole number.\r<BR>\n" );
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document.write( "1/3 of this is (1/3)*90 = 30 ball bearings.\r<BR>\n" );
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document.write( "x = weight of the empty box<BR>\n" );
document.write( "b = weight of 30 ball bearings<BR>\n" );
document.write( "3b = weight of 90 ball bearings<BR>\n" );
document.write( "All weight expressions are in pounds.\r<BR>\n" );
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document.write( "Based on the given info provided by your teacher, we can form these two equations<BR>\n" );
document.write( "x+3b = 21<BR>\n" );
document.write( "x+b = 9\r<BR>\n" );
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document.write( "Subtract the equations straight down<BR>\n" );
document.write( "The x terms cancel and we are left with this equation<BR>\n" );
document.write( "2b = 12<BR>\n" );
document.write( "It solves to b = 6 after dividing both sides by 2.\r<BR>\n" );
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document.write( "We can then say,<BR>\n" );
document.write( "x+b = 9<BR>\n" );
document.write( "x+6 = 9<BR>\n" );
document.write( "x = 9-6<BR>\n" );
document.write( "x = 3<BR>\n" );
document.write( "Or you could say<BR>\n" );
document.write( "x+3b = 21<BR>\n" );
document.write( "x+3*6 = 21<BR>\n" );
document.write( "x+18 = 21<BR>\n" );
document.write( "x = 21-18<BR>\n" );
document.write( "x = 3\r<BR>\n" );
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document.write( "Answer: B) 3 pounds<BR>\n" );
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