document.write( "Question 910531: Together John and Michael can paint a wall in 21 minutes. Alone John needs 11 minutes longer to paint the wall than× Michael needs. How much time does× John need to paint the wall by himself? Give your answer to the nearest tenth of a minute. \n" ); document.write( "
Algebra.Com's Answer #552530 by richwmiller(17219)\"\" \"About 
You can put this solution on YOUR website!
1/x+1/(x+11)=1/21
\n" ); document.write( "(21*x*(x+11))/x+(21*x*(x+11))/(x+11)=(21*x*(x+11))/21
\n" ); document.write( "(21*(x+11))+21*x=x*(x+11)
\n" ); document.write( "21*x+231+21*x=x^2+11*x
\n" ); document.write( "42*x+231=x^2+11*x
\n" ); document.write( "x^2-31*x-231=0
\n" ); document.write( "Can it be factored?
\n" ); document.write( "What factors of -231 add up to -31?
\n" ); document.write( "Nevertheless, we will complete the square
\n" ); document.write( "x^2-31*x=231
\n" ); document.write( "Add it.
\n" ); document.write( "x^2-31*x+(-31/2)=231+(-31/2)
\n" ); document.write( "Square it.
\n" ); document.write( "x^2-31*x+(961/4)=231+(961/4)
\n" ); document.write( "x^2-31*x+(240.25)=231+(240.25)
\n" ); document.write( "x^2-31*x+(240.25)=471.25
\n" ); document.write( "(x-15.5)^2=471.25
\n" ); document.write( "(x-15.5)^2=471.25
\n" ); document.write( "We will continue.
\n" ); document.write( "x+-15.5=(+-)21.7082933
\n" ); document.write( "x=15.5(+-)21.7082933
\n" ); document.write( "Positive useful answer:
\n" ); document.write( "x=15.5+21.7082933
\n" ); document.write( "One worker is x=37.2082933 or 37.2 minutes
\n" ); document.write( "x+11=11+37.2082933
\n" ); document.write( "x+11=48.2082933
\n" ); document.write( "Other worker =48.2082933 or 48.2 minutes
\n" ); document.write( "check
\n" ); document.write( "1/x+1/(x+11)=1/21
\n" ); document.write( "1/37.2082933+1/(37.2082933+11)=1/21
\n" ); document.write( "1/37.2082933+1/48.2082933=1/21
\n" ); document.write( "0.26875729e-1+0.20743319e-1=0.47619048e-1
\n" ); document.write( "0.47619048e-1=0.47619048e-1
\n" ); document.write( "ok\r
\n" ); document.write( "\n" ); document.write( "Useless answer:
\n" ); document.write( "x=15.5-21.7082933
\n" ); document.write( "Useless answer is x=-6.20829335
\n" ); document.write( " x =-6.20829335
\n" ); document.write( " This answer is useless because it is Negative
\n" ); document.write( "For real life cases involving time, distance and other measurements, we reject the negative results
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