document.write( "Question 548491: one pipe can fill a cooling tank in 3 hours less that a second pipecan.if the two pipes together can fill seven-ninths of the tank in 4 hours ,how many hours would it take each pipe alone to fill the tank \n" ); document.write( "
Algebra.Com's Answer #357023 by ankor@dixie-net.com(22740)\"\" \"About 
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one pipe can fill a cooling tank in 3 hours less that a second pipe can.
\n" ); document.write( "if the two pipes together can fill seven-ninths of the tank in 4 hours,
\n" ); document.write( "how many hours would it take each pipe alone to fill the tank
\n" ); document.write( ":
\n" ); document.write( "Let p = one pipes filling time
\n" ); document.write( "then
\n" ); document.write( "(p+3) = another pipes filling time
\n" ); document.write( ":
\n" ); document.write( "Let a full tank = 1
\n" ); document.write( ":
\n" ); document.write( "\"4%2Fp\" + \"4%2F%28%28p%2B3%29%29\" = \"7%2F9\"
\n" ); document.write( "Multiply by 9p(p+3), results
\n" ); document.write( "9(p+3)(4) + 9p(4) = 7p(p+3)
\n" ); document.write( "36p + 108 + 36p = 7p^2 + 21p
\n" ); document.write( "72p + 108 = 7p^2 + 21p
\n" ); document.write( ":
\n" ); document.write( "combine like terms on the right
\n" ); document.write( "0 = 7p^2 + 21p - 72p - 108
\n" ); document.write( "7p^2 - 51p - 108 = 0; a quadratic equation
\n" ); document.write( "You can use the quadratic equation here, but this will factor to:
\n" ); document.write( "(7p + 12)(p - 9) = 0
\n" ); document.write( "the positive solution is all we want here
\n" ); document.write( "p = 9 hrs time for one pipe alone
\n" ); document.write( "and
\n" ); document.write( "12 hrs for the other pipe alone
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Let's check this out, using decimals
\n" ); document.write( "\"4%2F9\" + \"4%2F12\" =
\n" ); document.write( ".444 + .333 = .777 which is very close to 7/9 \n" ); document.write( "
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