### Instruction: A man invests Rs. 3,000 at the rate of 5% per annum. How much more should he invest at the rate of 8%, so that he can earn a total of 6% per annum?
Answer Choices: (A) Rs. 1200 (B) Rs. 1300 (C) Rs. 1500 (D) Rs. 2000 (E) None of these.### Response: Let's solve the multi-choice question step by step.
Interest on Rs.3000 at 5% per annum = ( 3000 × 5 × 1) / 100 = Rs. 150
Let his additional investment at 8% = x
Interest on Rs.x at 8% per annum = ( x × 8 × 1 ) / 100 = 2x/25.
To earn 6% per annum for the total, interest = (3000 + x) × 6 × 1/100.
=> 150 + 2x/25 = (3000 + x) × 6 × 1/100.
=> 15000 + 8x = (3000 + x) × 6.
=> 15000 + 8x = 18000 + 6x.
=> 2x=3000.
=> x=1500.
The answer is C