Answer:
9 days
Step-by-step explanation:
Given isabella saves a nickel a day.From this day onwards she kept on incresing the savings by doubling them.
Here it form's a geometric progression with first term(a) = 1 and common ratio (r) = 2
S(n) = [tex]a(\frac{r^{n}-1 }{r-1} )[/tex]
Given condition is S(n) >500
[tex]\frac{2^{n}-1 }{2-1}>500[/tex]
[tex]2^{n}>501[/tex]
n ≥ 9
So it will take 9 days for her savings to be more than 500
