Chapter 2 - Section 2.1 - Simple Interest - Exercises - Page 133: 30

$ 60.606\%$

Given PV=$\$ 99$ The interest ( the fee) is $\$ 10,$ The time must be in years (t=2 months$=\displaystyle \frac{2}{12}=\frac{1}{6}$ year) we need r: $\mathrm{I}\mathrm{N}\mathrm{T}=\mathrm{P}\mathrm{V}(\mathrm{r}\mathrm{t})\qquad$/$\div(PV\cdot t)$ $ r=\displaystyle \frac{INT}{PV\cdot t}=\frac{10}{99\cdot\frac{1}{6}}\approx$0.606060606061 $ 60.606\%$