R alone can do a work in 12 days working 4 hours a day. S alone can do the same work in 6 days working 8 hours a day. How many hours do they need to work together in a day to complete the same work in 4 days?
Show answer & explanation
Correct answer: B
Explanation
R's total work = 12 × 4 = 48 hours
S's total work = 6 × 8 = 48 hours
Total work = 48 units
Time required per day to complete the work in 4 days = 48 / (4 × 2)= 6 hours