Twenty persons take 15 days to complete a certain work working 8 hours a day. To complete the same work in 4 days, the number of hours a day 60 persons should work is:
Answer
The correct answer is C: 10. Using M₁D₁H₁ = M₂D₂H₂: 20×15×8 = 60×4×H₂ → 2400 = 240×H₂ → H₂ = 10 hours.