How Much Time will They Take to Complete The Work?
Answer: (4) 4 hours
A can complete a piece of work = 6 hours
A can work in an hour = 1/6
B can complete the same work = 12 hours
Then, B can work in an hour = 1/12
Therefore, A and B can together the in an hour = 1/6 + 1/12
= (2 + 1) /12
Then, A and B can together complete the work = 4 hours
Hence, the answer is (4) 4 hours.