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by dreamv » Tue Feb 21, 2012 2:43 pm
Working alone at its own constant rate, a machine seals K cartons in 8 hours, and working alon at its own constant rate, a second machine seals K cartons in 4 hours. If the two machines, each working at its won constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?

A. 25%
B. 33 and 1/3 %
C. 50%
D. 66 and 2/3 %
E. 75%
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Source: — Problem Solving |

by pemdas » Tue Feb 21, 2012 3:09 pm
two machines, X and Y
their speeds, X speed 1/8 and Y speed 1/4 (the speed of Y greater)
combined speed by X&Y will be (1/4 +1/8)=3/8
find the required, i.e. ratio faster speed machine(Y)/combined speed machines(X&Y)=1/4 : 3/8=1/4 *8/3=2/3 or 66%
d
dreamv wrote:Working alone at its own constant rate, a machine seals K cartons in 8 hours, and working alon at its own constant rate, a second machine seals K cartons in 4 hours. If the two machines, each working at its won constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?

A. 25%
B. 33 and 1/3 %
C. 50%
D. 66 and 2/3 %
E. 75%
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by GMATGuruNY » Tue Feb 21, 2012 4:33 pm
dreamv wrote:Working alone at its own constant rate, a machine seals K cartons in 8 hours, and working alon at its own constant rate, a second machine seals K cartons in 4 hours. If the two machines, each working at its won constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?

A. 25%
B. 33 and 1/3 %
C. 50%
D. 66 and 2/3 %
E. 75%
The slower machine takes TWICE AS LONG to produce K cartons.
TWICE AS LONG means HALF AS FAST.
Thus, for every 2 cartons produced by the faster machine, the slower machine produces 1 carton.
Thus, of every 3 cartons produced, the fraction produced by the faster machine = 2/3 = 66 2/3%.

The correct answer is D.
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