The population of bats will be 3000 between the years 2021 and 2022.
Explanation:
Step 1; It is given that the bats' population decreases to a half every year. So if there were 300,000 bats in 2015 there would be 150,000 bats in 2016. In the year 2017, there would be half of what there was in 2016 i.e. half of 150,000 bats. Similarly, we calculate the number of bats every year. If we reduce the bats' population to a half every year we get it as such
Bats in the year 2015 - 300,000
Bats in the year 2016 - 150,000
Bats in the year 2017 - 75,000
Bats in the year 2018 - 37,500
Bats in the year 2019 - 18,750
Bats in the year 2020 - 9,375
Bats in the year 2021 - 4,688
Bats in the year 2022 - 2,344
Step 2; We need to see the number of bats every year and check what year the population reached 3000. In the year 2021, there will be 4,688 and in the year 2022, there will be 2,344. So somewhere between the years of 2021 and 2022, the bats' population will reach 3,000.