AFCAT I 23 Jan 2025 Shift 2 Paper

Total work = time × efficiency
Calculation:
Let the capacity of the tank (work to be done) be 24 x units (LCM of 6,8,12 )
⇒ The efficiency of pipe A=24x∕6=4x units/day
⇒ Efficiency of pipe B = 24x/8 = 3x units/day
⇒ Efficiency of pipe (A+B+C)=24x∕12=2x units/day
⇒ Efficiency of pipe C = efficiency of (A+B =C) - efficiency of (A+B)
Efficiency of pipe C=2x−(4x+3x)=−5x units/day
Negative efficiency implies that pipe C is emptying pipe.
⇒ Time taken by pipe C to empty the filled tank=24x∕5x
=4.8 hours or 4 hrs 48 min
∴ The pipe C will empty the tank in 4 hrs 48 mins.