A lake has a small population of a rare endangered fish. The lake currently has a population of 10 fish. The number of fish is increasing at a rate of 4% per year. When will the population double? How long will it take the population to be 80 fish?

Respuesta :

Answer: 1) After 17.673 years ( Approx) the population will be doubled.

2) After 53.019 years the population will be 80.

Step-by-step explanation:

1) Let x represents the number of years after which the population will doubled,

Since rate of interest = 4%

And, initial number of fish = 10,

Hence the fish after x years = [tex]10(1+\frac{4}{100})^x =10(1+0.04)^x =10(1.04)^x[/tex]

⇒ [tex]10(1.04)^x = 20[/tex]

⇒ [tex](1.04)^x = 2[/tex]

⇒ [tex]x log (1.04) = log(2)[/tex]

⇒ [tex]x = \frac{log(2)}{log(1.04)}=17.6729877\approx 17.673[/tex]

Hence, After 17.673 years ( Approx) the population will be doubled.

2) Let after y years the population will be 80.

⇒ [tex]10(1.04)^x = 80[/tex]

⇒ [tex](1.04)^x = 8[/tex]

⇒ [tex]x log (1.04) = log(8)[/tex]

⇒ [tex]x = \frac{log(8)}{log(1.04)}=53.0189631\approx 53.019[/tex]

Hence, After 53.019 years the population will be 80.