Simple Interest

Rajesh gave 1200 on loan. Some amount he gave at 4% per annum on simple interest and remaining at 5% per annum on simple interest. After two years, he got 110 as interest. Then the amounts given at 4% and 5% per annum on simple interest are, respectively

If a sum of money at a certain rate of simple interest per year doubles in 5 years and at a different rate of simple interest per year becomes three times in 12 years, then the difference in the two rates of simple interest per year is

Same principal is invested in schemes of compound interest and simple interest. The interest obtained in simple interest and compound interest schemes after 2 years are Rs 1200 and Rs 1290 respectively. If the rate of interest is 15%, then what is the principal (in Rs)?