document.write( "Question 937192: A new water pump has a capacity of 60 m3/day. If its capacity goes down by 15% every year, in how many years will the capacity go down to 20 m3/day? -Differential Equation Problem \n" ); document.write( "

Algebra.Com's Answer #570654 by Alan3354(69443) $\"\"$ $\"About$

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A new water pump has a capacity of 60 m3/day. If its capacity goes down by 15% every year, in how many years will the capacity go down to 20 m3/day?
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\n" ); document.write( "Each year its capacity is 85% of the previous year.
\n" ); document.write( "C = 60*0.85^t --- t in years
\n" ); document.write( "20 = 60*0.85^t
\n" ); document.write( "1/3 = 0.85^t
\n" ); document.write( "log(1/3) = t*log(0.85)
\n" ); document.write( "t = log(1/3)/log(0.85)
\n" ); document.write( "t =~ 6.76 years \n" ); document.write( "

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