Question 1113289
{{{1/x+1/(x-4)=1/8}}}

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{{{8(x-4)+8x=x(x-4)}}}

{{{8x-32+8x=x^2-4x}}}

{{{x^2-4x-16x+32=0}}}

{{{x^2-20x+32=0}}}


{{{x=(20+- sqrt(400-4*32))/2}}}

{{{x=(20+- sqrt(272))/2}}}

{{{x=(20+- sqrt(16*17))/2}}}

{{{x=10+- 2*sqrt(17)}}}

Must use the greater value.

{{{x=10+2*sqrt(17)=18.2462}}}--------time in hours for smaller pipe;
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18.2 hours (nearest tenth of hour)