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The Donald Rumsfeld problem

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by AleksandrM » Sun Jun 15, 2008 4:58 pm
I call this one the Donal Rumsfeld problem because there are many unknowns.

Machine A and Machine B can produce 1 widget in 3 hours working together at their respective constant rates. If Machine A's speed were doubled, the two machines could produce 1 widget in 2 hours working together at their respective rates. How many hours does it currently take Machine A to produce 1 widget on its own?

A) 1/2
B) 2
C) 3
D) 5
E) 6

Enjoy!
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by wawatan » Sun Jun 15, 2008 7:05 pm
is the answer e?
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by beeparoo » Sun Jun 15, 2008 7:06 pm
Can be solved in 30 sec or less. Ya trust me?

Eqn 1: R(A) + R(B) = 1/3 wid/hr

Eqn 2: 2R(A) + R(B) = 1/2 wid/hr <---Now perform elimination by subtracting Eqn 1 from Eqn 2.

R(B) swiftly cancels out.

R(A) = 1/2 - 1/3 = 1/6 wid/hr OR 6 hours to produce 1 widget.
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