document.write( "Question 1139010: A,B and C can do a job in 4 days . B can do it in 9 days and C can do it in 8 days . How long would it take A to do it himself ? \n" ); document.write( "

Algebra.Com's Answer #756799 by VFBundy(438) $\"\"$ $\"About$

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A, B, and C, working together, can do 1/4 of the job per day.
\n" ); document.write( "A, working alone, can do 1/A of the job per day. (We are trying to figure out what A is.)
\n" ); document.write( "B, working alone, can do 1/9 of the job per day.
\n" ); document.write( "C, working alone, can do 1/8 of the job per day.
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\n" ); document.write( "\"A, B, and C, working together, can do 1/4 of the job per day.\":
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\n" ); document.write( "1/A + 1/9 + 1/8 = 1/4
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\n" ); document.write( "Common denominator for left side of equation is: (A)(9)(8) = 72A
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\n" ); document.write( "Set up the equation using 72A as common denominator on left side of equation, then simplify:
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\n" ); document.write( "(1*9*8)/72A + (1*8*A)/72A + (1*9*A)/72A = 1/4
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\n" ); document.write( "72/72A + 8A/72A + 9A/72A = 1/4
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\n" ); document.write( "(72 + 8A + 9A)/72A = 1/4
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\n" ); document.write( "(72 + 17A)/72A = 1/4
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\n" ); document.write( "Cross-multiply:
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\n" ); document.write( "4(72 + 17A) = 1(72A)
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\n" ); document.write( "Simplify:
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\n" ); document.write( "288 + 68A = 72A
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\n" ); document.write( "288 = 4A
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\n" ); document.write( "A = 72
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\n" ); document.write( "It will take A 72 days to do the job himself. \n" ); document.write( "

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