9514 1404 393
Answer:
A = 500
B = 1.04
49.6 years
Step-by-step explanation:
We assume your 'A' and 'B' refer to parameters in an exponential formula of the form ...
y = A·B^x
In this form, A is the initial investment value, $500. B is the growth factor, 1+4% = 1.04, assuming interest is compounded annually. We want to find x such that y=$3500.
3500 = 500·1.04^x . . . . . fill in known values
7 = 1.04^x . . . . . . . . . . . . . divide by 500
log(7) = x·log(1.04) . . . . . . take logarithms
x = log(7)/log(1.04) ≈ 49.61 . . . . divide by the coefficient of x
It will take about 49.6 years for there to be $3500 in Mrs. Williams's account.
