In 2010, a city's population was 1,405,233 and it was decreasing at a rate of 1.1%. At this rate when will the city's population fall below 1,200,000?
a. 2024
b. 2027
c. 2036
d. 2049

Respuesta :

The equation
                                            P(t) = 1405233 * (1 - 0.011)^(t)
models the population at t years after 2010. Then, when P(t) = 1,200,000, we have
                                 1200000 = 1405233 * (0.989)^t
                                  (0.989)^t = 1200000/1405233
                                                t = log(1200000/1405233)/log(0.989)
                                                t = 14.27 years
This means 14.27 years after 2010. Therefore, the answer to this question is 2024.

A log function is a way to find how much a number must be raised in order to get the desired number. The population of the city will be 1,200,000 in the year 2024.

What is Logarithm?

A log function is a way to find how much a number must be raised in order to get the desired number.

[tex]a^c =b[/tex]

can be written as

[tex]\rm{log_ab=c[/tex]

where a is the base to which the power is to be raised,

b is the desired number that we want when power is to be raised,

c is the power that must be raised to a to get b.

For example, let's assume we need to raise the power for 10 to make it 1000 in this case log will help us to know that the power must be raised by 3.

The decrease in the population of the city can be written as,

[tex]\rm Final\ population=(Initial\ population)\times (1-r)^n[/tex]

[tex]1,200,000=1,405,233(1-0.011)^n\\\\0.8539=(0.989)^n\\\\\rm log(0.8539)=n\ log(0.989)\\\\n= \dfrac{log(0.8539)}{log(0.989)}\\\\n=14.279 \approx 14.3[/tex]

Since the initial population was 1,405,000 in the year 2010, then the population of the 1,200,000 will be 14 years later.

Thus, the population of the city will be 1,200,000 in the year 2024.

Learn more about Logarithm:

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