Population growth

How many people will be on Earth from two people for 5,000 years if every couple always has four children (2 boys and two girls) at the age of 25-35, and every man will live 75 years?

Correct answer:

s =  4.820814132777E+60

Step-by-step explanation:

$$\begin{gathered} n_0=2 \\ {n}_{35}=n_0+1\cdot 4=2+1\cdot 4=6 \\ {n}_{75}=n_{35}-2+2\cdot 4=6-2+2\cdot 4=12 \\ {n}_{100}=n_{75}-4+4\cdot 4=12-4+4\cdot 4=24 \\ {a}_1=n_{35}=6 \\ {a}_2=n_{75}=12 \\ {a}_3=n_{100}=24 \\ q=a_2/a_1=12/6=2 \\ q=a_3/a_2 \\ n=5000/25-1=199 \\ s=a_1\cdot q^n=6\cdot 2^{199}=4.820814132777\cdot 10^{60} \end{gathered}$$

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