document.write( "Question 411440: A large pipe can fill a tank in 10 minutes, and a smaller pipe can fill the tank in 20 minutes. How long will it take to fill the tank if the both pipes are used at the same time?\r
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Algebra.Com's Answer #289200 by sudhanshu_kmr(1152)\"\" \"About 
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if both pipes are used then in one minute tank will fill ( 1/10 - 1/20 ) portion\r
\n" ); document.write( "\n" ); document.write( "it is 1/20 portion...\r
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\n" ); document.write( "\n" ); document.write( "as 1/20 portion of tank fill in 1 minute.\r
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\n" ); document.write( "\n" ); document.write( "so, for 1 complete portion 1 / (1/20) = 20 \r
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\n" ); document.write( "\n" ); document.write( "so, 20 minutes..... \r
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