SOLUTION: An experienced teaching assistant can grade all exams for a calculus class 3 hours faster than a new teaching assistant. Working together, the teaching assistants can grade all the

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Question 1118974: An experienced teaching assistant can grade all exams for a calculus class 3 hours faster than a new teaching assistant. Working together, the teaching assistants can grade all the exams for the calculus class in 5 hours. How long would it take for the new teaching assistant to grade all of the exams for the calculus class alone?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
x, time for new assistant to grade the papers if working alone

1%2F%28x-3%29%2B1%2Fx=1%2F5
--
5x%2B5x-15=x%5E2-3x
10x-15=x%5E2-3x
x%5E2-13x%2B15=0
general_quadratic_formula_solution
x=%2813%2Bsqrt%28109%29%29%2F2

x=11.72
11 hours 43 minutes

check:-----------
1%2F8.72%2B1%2F11.72=1%2F5
0.1147%2B0.0853
0.2, yes