6554
Assuming that the growth the function will be of the form
f(n) = P*R^n
where
P = Initial population
R = Growth rate per period
n = number of periods
In this problem, the only period or interval I see are days. So we'll use n to represent the number of days since the start. The initial population is 1000, and the ratio would be 1600/1000 = 1.6. So the formula becomes
f(n) = 1000*1.6^n
So let's evaluate that function using n=4.
f(n) = 1000*1.6^n
f(4) = 1000*1.6^4
f(4) = 1000*6.5536
f(4) = 6553.6
Since we can't have a fractional mosquito, round to the nearest integer, giving 6554.
