Correct Answer: Option C
Whole work is done by A in (20 x (5/4)) = 25 days.
Now, (1 – 4/5) i.e., 1/5 work is done by A and B in 3 days.
Whole work will be done by A and B in (3 x 5) = 15 days.
A's 1 day's work = 1/25, (A + B)'s 1 day's work = 1/15
Therefore, B's 1 day's work = (1/15 – 1/25) = 4/150 = 2/75.
So, B alone would do the work in 75/2 = 37(1/2) days.
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