Answer: 4.025 acres.
Explanation:
Given: The builder buys 16.1 acres of land to develop a new set of walking trails and baseball fields.
Thus, the total land he has =16.2 acres
If the builder plans to use 0 .25 of the land for baseball.
Then the land will be used for baseball

Hence, only 4.025 acres of the land will be used for baseball.