document.write( "Question 1177723: It takes pump A 2 hours less time than pump B to empty a pool. Pump A is started at 8:00am and pump B at 10:00am. At 12:00pm 60% of the pool.is empty when pump B broke down. How much time after 12:00pm would it take pump A to empty the pool? \n" ); document.write( "
Algebra.Com's Answer #806852 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "let x = # hours A takes alone to empty the pool
\n" ); document.write( "then x+2 = # hours B takes alone

\n" ); document.write( "1/x = fraction of job A does in 1 hour
\n" ); document.write( "1(x+2) = fraction of job B does in 1 hour

\n" ); document.write( "At 12pm when pump B broke down, A has been working 4 hours and B 2 hours. The fraction of the job done at that time is

\n" ); document.write( "\"4%281%2Fx%29%2B2%281%2F%28x%2B2%29%29\"

\n" ); document.write( "That fraction of the job done at 12pm is 60% = 3/5. Solve that equation to find out how many hours A takes to empty the pool alone.

\n" ); document.write( "\"4%281%2Fx%29%2B2%281%2F%28x%2B2%29%29+=+3%2F5\"

\n" ); document.write( "Multiply through by the least common denominator \"5%28x%29%28x%2B2%29\"

\n" ); document.write( "\"20%28x%2B2%29%2B10%28x%29=3%28x%29%28x%2B2%29\"
\n" ); document.write( "\"30x%2B40+=+3x%5E2%2B6x\"
\n" ); document.write( "\"3x%5E2-24x-40+=+0\"

\n" ); document.write( "This does not factor; use the quadratic formula and of course use the positive root.

\n" ); document.write( "\"x+=+%2824%2Bsqrt%281056%29%29%2F6\" = 9.416 to 3 decimal places.

\n" ); document.write( "2/5 of the pool remains to be emptied; the number of hours it will take A to finish is

\n" ); document.write( "\"9.416%2A0.4+=+3.7664\"

\n" ); document.write( "ANSWER: to a few decimal places, 3.7664 hours
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