Tap A can fill an empty tank alone in 6 hours. Tap B alone can empty the same tank, when filled, in 8 hours. If they are opened in alternate hours starting with A, then in how much time will the tank be full for the first time?
Answer & explanation
Correct answer: option 3
A+ = 6 hrs, B- = 8 hrs,
⇒ They are opened on alternate hours,
1st hour = +4 units
2nd hour = - 3 units,
Every 2 hours, 1 units is filled,
So, in 40 hours, 20 units is filled,
Therefore in 41 hours, 24 units are filled.