Tap ‘A’ can fill a water tank in 25 minutes, tap ‘B’ can fill the same tank in 40 minutes and tap ‘C’ can empty that tank in 30 minutes. If all the three taps are opened together, in how many minutes will the tank be completely filled up or emptied? Choose the correct answer:
A) 3 2⁄13  B) 15 5⁄13  C) 8 2⁄13  D) 31 11⁄19  E) None of these
Tank filled in 1 minute = 1⁄25 + 1⁄40 - 1⁄30 part   = 24+15−20/600=19/600 part   ∴ tank will be filled complete in minutes   = 600⁄19 = 3111⁄19   Answer 31 11⁄19
<result>D</result>
Tap ‘A’ can fill a water tank in 25 minutes, tap ‘B’ can fill the same tank in 40 minutes and tap ‘C’ can empty that tank in 30 minutes. If all the three taps are opened together, in how many minutes will the tank be completely filled up or emptied?