A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?	Choose the correct choice from the following.
A) 10 days
B) 11 days
C) 13 days
D) 15 days
E) 12 days
Let us assume the total work to be done is 60 units.   According to the question,   A and B finish the work in 12 days working together which implies 5 units of work is done by them in a single day, i.e,   A + B = 5 ----- (1)   Also, we know A alone can finish the work in 20 days which implies he can do 3 units of work in a single day.   Hence, B’s one day work is   3 + B = 5   =&gt; B = 2.   But B works half a day only which implies he is doing only 1 unit of work in a single day and hence only 4 units of work is done in a single day.   Thus, total number of days taken by A and B working together to complete the work is   60/4= 
<gadget id="calculator">  60/4</gadget>
<output>15</output>
15 days.   ANSWER:15 days
<result>D</result>
A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?