If 16 new lotus plants are added through reproduction in a pond where there were 40 lotus plants last year, the birth rate in the population is ______ offspring per lotus per year.

If 16 new lotus plants are added through reproduction in a pond where there were 40 lotus plants last year, the birth rate in the population is 0.4 offspring per lotus per year.

40 --- 16 $\frac{1\times 16}{40}=\frac{16}{40}=0.4$