doubling time
[tex]A=P(2)^\frac{n}{d}[/tex]
A=final amount
P=initial amount
n=number of days
d=number of days to double
so
given initial is 40 ants
doubling time is 10 days
and days we want is 20 then
[tex]A=40(2)^\frac{20}{10}[/tex]
[tex]A=40(2)^2[/tex]
[tex]A=40(4)[/tex]
A=160
the population is 160