Final answer:
When pipe B is used for half the time and pipes A and B fill the tanker together for the other half, it will take 24 minutes to fill the tanker.
Step-by-step explanation:
To find how many minutes it will take to fill the tanker when pipe B is used for half the time and pipes A and B fill it together for the other half, we need to calculate the rate at which each pipe fills the tanker.
Let's assume the tanker has a capacity of 1 unit.
The rate at which pipe A fills the tanker is 1 unit per 60 minutes, which is 1/60 units per minute.
The rate at which pipe B fills the tanker is 1 unit per 40 minutes, which is 1/40 units per minute.
Now, let's consider the time when B is used for half the time and A and B fill it together for the other half. In this case, B will be used for 30 minutes and A and B will fill the tanker together for 30 minutes.
In 30 minutes, the combined rate of A and B is (1/60 + 1/40) units per minute, which is (1/60 + 3/120) or (1/60 + 1/40) units per minute. Simplifying, we get (1/60 + 1/40) = (2/120 + 3/120) = 5/120 units per minute, which is 1/24 units per minute.
Since the tanker has a capacity of 1 unit, it will take (1 unit) รท (1/24 units per minute) = 24 minutes to fill the tanker when B is used for half the time and A and B fill it together for the other half.
Therefore, the answer is 24 minutes.