document.write( "Question 374254: Water is leaking from a tank at a constant rate of 20% per hour. If yn denotes the amount of water at the beginning of the hour, in how many hours would Yn ≤ y1/10? \n" ); document.write( "
Algebra.Com's Answer #266353 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
I take this to mean the water left in the tank
\n" ); document.write( "is less than or equal to 1/10 of the starting
\n" ); document.write( "amount of water after \"n\" hours
\n" ); document.write( "after 1st hour: \"y%5B1%5D+-+.2y%5B1%5D+=+.8y%5B1%5D\"
\n" ); document.write( "after 2nd hour: \".8y%5B1%5D+-+.2%2A.8y%5B1%5D+=+.8%5E2%2Ay%5B1%5D\"
\n" ); document.write( "after 3rd hour: \".8%5E2%2Ay%5B1%5D+-+.2%2A.8%5E2%5B1%5D+=+.8%5E3%2Ay%5B1%5D\"
\n" ); document.write( "The pattern here is that after \"n\" hours,
\n" ); document.write( "the amount of water left in the tank is
\n" ); document.write( "\".8%5En%2Ay%5B1%5D\"
\n" ); document.write( "The problem wants to know when \".8%5En%2Ay%5B1%5D+%3C=+%281%2F10%29%2Ay%5B1%5D\"
\n" ); document.write( "The \"y%5B1%5D\"'s cancel from both sides leaving:
\n" ); document.write( "\".8%5En+%3C=+1%2F10\"
\n" ); document.write( "\"10%2A%28.8%5En%29+%3C=+1\"
\n" ); document.write( "Note that \".8%5En+=+8%5En%2A10%5E%28-n%29\"
\n" ); document.write( "\"10%2A10%5E%28-n%29%2A+8%5En+%3C=+1\"
\n" ); document.write( "\"10%5E%28-n+%2B+1%29%2A8%5En+%3C=+1\"
\n" ); document.write( "Take the log base 10 of both sides
\n" ); document.write( "\"1+-+n+%2B+n%2Alog%288%29+%3C=+0\"
\n" ); document.write( "\"n%2A%28log%288%29+-+1%29+%3C=+-1\"
\n" ); document.write( "Now I need to multiply both sides by
\n" ); document.write( "\"-1\" which reverses the < sign
\n" ); document.write( "\"n+%3E=+1%2F%281+-+log%288%29%29\"
\n" ); document.write( "\"n+%3E=+1%2F%281+-+.90309%29\"
\n" ); document.write( "\"n+%3E=+1%2F.09691\"
\n" ); document.write( "\"n+%3E=+10.3189\"
\n" ); document.write( "Or, \"n+%3E=+10\" in whole numbers
\n" ); document.write( "The answer is
\n" ); document.write( "\"y%5B10%5D+%3C=+%281%2F10%29%2Ay%5B1%5D\"
\n" ); document.write( "Unless I messed up- I think the approach is right\r
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