Answer
1.73 years
Work Step by Step
We now consider how long it takes to earn 200 dollars in interest if 1200 dollars is invested at 9 percent compounded quarterly.
$$ 1400 = 1200(1+.09/4)^{4t}$$
$$ 4t = log_{.0225}(7/6)$$
$$t=7.3 \ years$$
1.73 years
