A sum of Rs. 1550 was lent partly at 5% and partly at 8% simple interest. The total interest received after 3 years is Rs. 300. The ratio of money lent at 5% to that at 8% is = ?

Explanation:-

Let the sum at 8% be Rs. x.
Let the sum at 5% be 1550 - x.
According to the given condition,
$$\eqalign{ & \frac{{{\text{x}} \times 8 \times 3}}{{100}} + \frac{{\left( {1550 - {\text{x}}} \right) \times 5 \times 3}}{{100}} = 300 \cr & \Rightarrow \frac{{24{\text{x}} + \left( {1550 - {\text{x}}} \right) \times 15}}{{100}} = 300 \cr & \Rightarrow \frac{{24{\text{x}} + 23250 - 15{\text{x}}}}{{100}} = 300 \cr & \Rightarrow 24{\text{x}} - 15{\text{x}} = 30000 - 23250 \cr & \Rightarrow 24{\text{x}} - 15{\text{x}} = 6750 \cr & \Rightarrow 9{\text{x}} = 6750 \cr & \Rightarrow {\text{x}} = \frac{{6750}}{9} = 750 \cr & \frac{{{\text{Money lent at 5}}\% }}{{{\text{Money lent at 8}}\% }} \cr & = \frac{{1550 - 750}}{{750}} \cr & = \frac{{800}}{{750}} \cr & = \frac{{16}}{{15}} \cr}$$