Mr. Pinto invests one-fifth of his capital at 6%, one-third at 10% and the remaining at 1%, each rate being si

Question

Mr. Pinto invests one-fifth of his capital at 6%, one-third at 10% and the remaining at 1%, each rate being simple interest per annum. Then, the minimum number of years required for the cumulative interest income from these investments to equal or exceed his initial capital is

Accepted Answer

Let the total investment me 15x and the no. of years required be T years ( 3 x × 6 × T ) 100 + ( 5 x × 10 × T ) 100 + ( 7 x × 1 × T ) 100 ≥ 15 x \frac{\left(3x	imes6	imes Tight)}{100}+\frac{\left(5x	imes10	imes Tight)}{100}+\frac{\left(7x	imes1	imes Tight)}{100}\ge15x 100 ( 3 x × 6 × T )