Answer:469 million
Explanation:
Given
The population of a country at t=1900 is 420 million
and P'(t) is a constant therefore P(t) is a linear function of time
assuming P(t)=7t +c
at t=0 i.e. 1900 at starting Point P(t)=420 million
i.e.
![420=7* 0+c](https://img.qammunity.org/2020/formulas/mathematics/high-school/gujvlhoepgk4e9lc8s0ubo78gl3cg5ipte.png)
![c=420 million](https://img.qammunity.org/2020/formulas/mathematics/high-school/ly44vuyw2kkefkx1dfzonykrtz556mvxdc.png)
Thus
![at\ t=7\ year\ later\ i.e.\ 1907](https://img.qammunity.org/2020/formulas/mathematics/high-school/amfjji8xg6kw09dc2j9plicpbciaadw9cj.png)
![P(t)=7* 7+420=469 million](https://img.qammunity.org/2020/formulas/mathematics/high-school/xcadp5brpa8zcrunfsf720atrrsdrb8qbj.png)
Thus at 1907 Population is 469 million
P'(t)=7 indicates that growth rate of Population is constant equals to 7 billion