A completes 80% of a work in 20 days. Then B also joins and A and B together finish the remaining work in 3 days. How long does it need for B if he alone completes the work?  Pick one.
A) 35 Days  B) 36.5 Days  C) 37 Days  D) 37.5 Days  E) 38 Days
Work done by A in 20 days = 80/100 = 8/10 = 4/5   Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 --- (1)   Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)   Work done by A and B in 1 day = 1/15 ---(2)   Work done by B in 1 day = 1/15 – 1/25 = 2/75   =&gt; B can complete the work in 75/2 days = 37 ½ days   Answer is 37.5 Days.
<result>D</result>
A completes 80% of a work in 20 days. Then B also joins and A and B together finish the remaining work in 3 days. How long does it need for B if he alone completes the work?