There are many ways to solve a problem like this. Guessing that averaging will do it is not one of them. Do you have a specific reason to think it would help? If so, then that would be worth considering. (By the way, the average of 2 and 3 is not 5, anyway.)

One way is to think about

*how far apart* they are when B starts, and how fast the

*distance between* them is decreasing.

Another is to write an expression for the distance between them at time t seconds after B starts, and use that to write an

equation you can solve (which will say, as you suggested, that the displacement of each of them after 60 seconds is equal). Using this algebraic method, a key is to clearly define what the variable, and any expression you write, means. (Your equation says that after 60 seconds, B will be where A was when B started, which is not quite what you want.)

If this is for a course you are taking, or from a textbook you are reading, can you find an example of a somewhat similar problem, and show us what method they used? You don't necessarily have to copy their method to solve it, but they probably are expecting you to be learning such a method, so you might as well do so!

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