This can be expressed as exponential growth of the form:
f=ir^t, f=final amount, i=initial amount, r=common ratio (rate), t=time
In this case we are given the point (2, 6500) and i=5000 so we can solve for the rate...
6500=5000r^2  divide both sides by 5000
1.3=r^2  take the square root of both sides and note that we know r>0
r=1.3^(1/2) so our equation becomes:
f=5000(1.3)^(1/2)^t  and knowing that (a^b)^c=a^(b*c) we can say:
f=5000(1.3)^(t/2)  so for t=18
f=5000(1.3)^9
f≈53022  (to nearest whole bacteria)
        
             
        
        
        
The worst case is when you pull 4 out and have 4 different colors. the 5th sock MUST match one of these. 5 is the answer
        
             
        
        
        
<span>86.8954776543 rounded to the nearest millionth is 86.895478
The order after the decimal point goes like this:
tenths, hundredths, thousandths, ten thousandths, hundred thousandths, millionth</span>
        
                    
             
        
        
        
X:     -2|   -1| 0|   1|   2|
y: 1.25| 2.5| 5| 10| 20|