X does 80% of a work in 20 days. He then calls in Y and they together finish the remaining work in 3 days. How long Y alone would take to do the whole work?
Choose the correct choice from the following answers
A) 37 1/2 B) 35 C) 36 D) 25 E) 34
Whole work is done by X in ( 20 x 5/4) = 25 days.   Now, ( 1 - 4 /5) i.e., 1/5	work is done by X and Y in 3 days.   Whole work will be done by X and Y in (3 x 5) = 15 days.   A's 1 day's work = 1 , (X + Y)'s 1 day's work = 1 .   25 15   Therefore Y's 1 day's work = ( 1/15	- 1 /25	) = 4/150 = 2/75   So, Y alone would do the work in 75/2	= 37 1/2 days.
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X does 80% of a work in 20 days. He then calls in Y and they together finish the remaining work in 3 days. How long Y alone would take to do the whole work?