Mathematics: At present, the population is 65.438+0.3 billion, the average childbearing age is 25 years old, and there are 654.38+0.5 children. The sex ratio is 654.38+0.00: 654.38+0.08, and the average life expectancy is 73 years old. How many people will there be in 20 years? The sex ratio is 100: 108.

Existing population1.300 million.

Assume that the number of people of all ages is evenly distributed.

Number of couples who can have children within 20 years

20/73* 13* 100/( 100+ 108)= 1.7 1

Giving birth1.71*1.5 = 2.56.

20-year death toll

13*20/73=3.56

Population in 20 years

13+2.56-3.56 =1200 million