document.write( "Question 1172077: Two questions;\r
\n" ); document.write( "\n" ); document.write( "(1) A resistor has a resistance of 30 ohms. What size resistor should be put with it, in parallel, to obtain a resistance of 3 ohms? (the answer is 10/3 ohms just need the work)\r
\n" ); document.write( "\n" ); document.write( "(2) The harmonic mean of two numbers, a and b, is a number M, such that the reciprocal of M is the average of the reciprocal of a and b. Find a formula for the harmonic mean. \n" ); document.write( "
Algebra.Com's Answer #796997 by ikleyn(52810)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "(1)  Let x be the unknown resistance.\r\n" );
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document.write( "     Then the effective resistance R satisfies this equation\r\n" );
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document.write( "        \"1%2FR\" = \"1%2F30\" + \"1%2Fx\".\r\n" );
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document.write( "     It gives you an equation to find x\r\n" );
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document.write( "        \"1%2F3\" = \"1%2F30\" + \"1%2Fx\",\r\n" );
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document.write( "     which implies\r\n" );
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document.write( "        \"1%2Fx\" = \"1%2F3\" - \"1%2F30\",   or\r\n" );
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document.write( "        \"1%2Fx\" = \"10%2F30\" - \"1%2F30\" = \"9%2F30\" = \"3%2F10\".\r\n" );
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document.write( "     Hence,  x = \"10%2F3\" ohms = 3.333 ohms.      ANSWER\r\n" );
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document.write( "(2)  The direct and literal translation of words into Math is this formula\r\n" );
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document.write( "         \"1%2FM\" = \"%281%2F2%29%2A%281%2Fa+%2B+1%2Fb%29\".\r\n" );
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document.write( "     From this formula,\r\n" );
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document.write( "          M = \"2%281%2F%281%2Fa+%2B+1%2Fb%29%29\" = \"%282ab%29%2F%28a+%2B+b%29\".    ANSWER\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved and explained.\r
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