Gauri went to the stationers and bought things worth Rs. 25, out of which 30 paise went on sales tax on taxable purchases. If the tax rate was 6%, then what was the cost of the tax free items?

Let the amount taxable purchases be Rs. x
$$\eqalign{ & {\text{Then}},6\% \,\,{\text{of}}\,x = \frac{{30}}{{100}} \cr & \Rightarrow x = {\frac{{30}}{{100}} \times \frac{{100}}{6}} = 5 \cr & \therefore {\text{Cost of tax free items}} \cr & = {\text{Rs}}{\text{.}}\left \cr & = {\text{Rs}}{\text{.}}\,19.70 \cr} $$