# The population of a given community of birds after 3 years

Arithmetic and Geometric progressions.

### The population of a given community of birds after 3 years

The population of a given community of birds after 3 years is 3million after 6years the population became 81million what is their first year population what is their 11th year population please help
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### Re: The population of a given community of birds after 3 yea

It is a geometric progression with common ratio 3. third year the population was $a_1q^2$

$a_13^2 =3$
$a_1 =3/9 million=1/3 million$

eleventh year was $\frac13*3^{10}$
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