Delhi Police Constable Exam Model Paper 1

Given:

A alone can complete a work in = 12 days
B alone can complete the same work in = 15 days
C alone can complete the same work in = 20 days
Formula:

Total work = Efficiency × Time
Calculation:


Total work = 60 units (LCM of 12, 15 and 20)
⇒ Efficiency of A = 60/12 = 5 units/day
⇒ Efficiency of B = 60/15 = 4 units/day
⇒ Efficiency of C = 60/20 = 3 units/day 60% of the total work = 60 × 60/100 = 36 units
∴ Time taken by A, B and C to complete 60% of the work = 36/(5 + 4 + 3) = 36/12 = 3 days