A Man Invested Some Money at 10% and 12%............. A person invested some money at 12% simple interest and some other amount at 10% simple interest. He received yearly interest of Rs.130. If he had interchanged the amounts, he would have received Rs. 40 more as yearly interest. How much did he invest at different rates?
$$0.12\cdot x+0.1\cdot y=130$$
and
$$0.12\cdot y+0.1\cdot x(=130+40)=170$$
Maybe you can solve.
Let the two invested rates be x and y.
Therefore, 12/100*x+10/100*y=130    (Dividing by 100)
          =0.12x+0.1y=130...(i)*0.12
0.1x+0.12y=170...(ii)*0.1
Now solve by yourself to get the answer.