ultrasound wrote:A is 80% as efficient as B. C does two-third of the work done by A and B together in the same time. If C alone does the work in 10 Days. Then A and C, together can do the work in........
(A) 12 days (B) 24 days
(C) 18 days (D) 6 Days
plz help me i m stuck in this question..
Let B's rate = 15 widgets per day.
Since A is 80% as efficient as B, A's rate = (80/100)(15) = (4/5)(15) = 12 widgets per day.
Combined rate for A and B = 15+12 = 27 widgets per day.
Since C does two-thirds of the work done by A and B, C's rate = (2/3)(27) = 18 widgets per day.
Since C completes the job in 10 days, the total job = (C's rate)(C's time) = (18)(10) = 180 widgets.
Combined rate for A and C = 12+18 = 30 widgets per day.
Time for A and C together to produce 180 widgets = w/r = 180/30 = 6 days.
The correct answer is
D.
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