Runners A and B practice in a round track going in opposite directions. Runner A takes 40 minutes to go once around the track. The two begin at the same time and meet every 15 minutes. How long does B take to go once around the track?

if B takes x minutes, then the two runners cover the entire track in 15 minutes.

1/40 + 1/x = 1/15

To solve this problem, we can use the concept of relative speed and time.

Let's assume that Runner B takes x minutes to go once around the track.

Since both runners meet every 15 minutes, we can form the equation:

Runner A's time + Runner B's time = Meeting time

40 minutes + x minutes = 15 minutes

Now, we can solve this equation to find the value of x:

40 + x = 15

x = 15 - 40

x = -25

From the equation, we can see that x = -25, which is not a valid answer for the time taken by Runner B. This suggests there might be an error in the problem statement.

A valid approach to solve this problem would be to re-evaluate the provided information and check for consistency or additional details.