Question

what is the meaning of ballpark figure?
asked for an estimate, the mayor provided a ballpark figure for the cost of expanding the washington public library.

a problem that leads to something good
a rough estimate for an amount

Explanation:

The phrase "ballpark figure" is an idiomatic expression. In English language usage, an idiom is a group of words established by usage as having a meaning not deducible from those of the individual words. Here, "ballpark" originally refers to the area where a baseball game is played. But in this context, when combined with "figure", it's used metaphorically. A "ballpark figure" is an approximate or rough estimate. It's not an exact calculation but a number that gives a general sense of the magnitude (like in the example where the mayor provided a ballpark figure for the cost - it's a rough idea of the amount, not the precise cost).

Answer:

A rough estimate for an amount.