In what time will the simple interest on Rs. 1750 at 9% per annum be the same as that on Rs. 2500 at 10.5% per annum in 4 years?

$$\eqalign{ & {\text{Let}}\,{\text{time}}\,{\text{is}}\,T\,{\text{years}}. \cr & {\text{According}}\,{\text{to}}\,{\text{questions}}, \cr & \frac{{1750 \times 9 \times T}}{{100}} = \frac{{\left( {2500 \times 10.5 \times 4} \right)}}{{100}} \cr & Or,\,T = \frac{{ {2500 \times 10.5 \times 4} }}{{1750 \times 9}} \cr & Or,\,T = 6.66 = 6\,{\text{years}}\,{\text{and}}\,8\,{\text{months}} \cr} $$