document.write( "Question 993340: A teacher and his assistant can grade all student's exams in 4 hours. When the assistant does the grading by himself, it takes him an hour longer than it takes the teacher alone to do the grading. Find how many hours it takes the teacher to do the grading by himself.\r
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Algebra.Com's Answer #613289 by Leesoski(1)\"\" \"About 
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1/t + 1/(t+1) = 1/4
\n" ); document.write( "4(x+1) + 4x = x(x+1)
\n" ); document.write( "4x+4+4x = x^2 + x
\n" ); document.write( "8x + 4 = x^2 + x
\n" ); document.write( "0=x^2 - 7x -4
\n" ); document.write( "Solve with quadratic function:
\n" ); document.write( "\"x=%287%2B-+sqrt%2865%29%29%2F2%29\"
\n" ); document.write( "X=7+8.1/2
\n" ); document.write( "X=7.5 (rounded to one decimal place)\r
\n" ); document.write( "\n" ); document.write( "The time it takes the teacher alone to grade the tests is 7.5 hrs\r
\n" ); document.write( "\n" ); document.write( "We check the answer by plugging into the original equation:
\n" ); document.write( "1/7.5 + 1/8.5 = 1/4
\n" ); document.write( "7.5/64 + 8.5/64 = 16/64
\n" ); document.write( "16/64 = 1/4
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