document.write( "Question 270192: A father and son can build a fence in 30 days. The father can finish the in 40 days. How many days are needed if the son was to put the fence himself? \n" ); document.write( "

Algebra.Com's Answer #197958 by drk(1908) $\"\"$ $\"About$

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The equation we need for this is
\n" ); document.write( "(1/f)(x) + (1/s)(x) = 1
\n" ); document.write( "where
\n" ); document.write( "f = father time
\n" ); document.write( "s = son time
\n" ); document.write( "x = time together
\n" ); document.write( "-----
\n" ); document.write( "we know that x = 30, f = 40. We get
\n" ); document.write( "(i) $\"%281%2F40%29%2A30+%2B+%281%2Fs%29%2A30+=+1\"$
\n" ); document.write( "step 1 -
\n" ); document.write( "multiply by the common denominator of 40s to get
\n" ); document.write( "(ii) $\"30s+%2B+1200+=+40s\"$
\n" ); document.write( "step 2- subtract s to get
\n" ); document.write( "(iii) $\"1200+=+10s\"$
\n" ); document.write( "step 3 - divide to get
\n" ); document.write( "(iv) $\"s+=+120\"$ \n" ); document.write( "

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