document.write( "Question 327637: A 4-square train is made with 13 toothpicks. A train is made with 400 toothpicks. How many squares are in the train?\r
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Algebra.Com's Answer #234687 by Edwin McCravy(20056) $\"\"$ $\"About$

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document.write( "Here is the 4-square train made with 13 toothpicks.\r\n" );
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document.write( "Notice that after the first toothpick, the green one below,\r\n" );
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document.write( "You place 3 more (red) toothpicks to form the first square.\r\n" );
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document.write( "Then you place 3 more red toothpicks to form the second square,\r\n" );
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document.write( "So after the first (green) toothpick, no matter how many squares\r\n" );
document.write( "you have made, it always takes 3 more (red) toothpicks to make the \r\n" );
document.write( "next square\r\n" );
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document.write( "So the sum is \r\n" );
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document.write( "toothpicks\r\n" );
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document.write( "If we have made n squares, we have added 3 a total of n times, so\r\n" );
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document.write( "Subtract 1 from both sides:\r\n" );
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document.write( "Divide by 3:\r\n" );
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document.write( "So we have mnade 133 squares, choice c. \r\n" );
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document.write( "Edwin

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