Srinivasan invests two equal amounts in two different banks. One bank offers simple interest at 8% per annum and the other offers simple interest at 12% per annum. At the end of one year, the total interest earned from both banks together is Rs. 1500. Find the amount invested in each bank.

Introduction / Context:
This problem deals with splitting an investment into two equal parts, each deposited at a different simple interest rate, and using the resulting total interest to find the size of each part. Many banking and aptitude questions require this type of reasoning, where equal principals at different rates generate a known total interest over a fixed time. Understanding how to model the total interest as a sum of two simple interest expressions is key.

Given Data / Assumptions:
Srinivasan invests the same amount in two banks.
Bank one offers 8 percent simple interest per annum.
Bank two offers 12 percent simple interest per annum.
The time period in both banks is one year.
Total interest from both banks together after one year is Rs. 1500.
We must find the amount invested in each bank, which are equal.

Concept / Approach:
Let the equal amount invested in each bank be P rupees. Simple interest from bank one for one year is P * 8 / 100, and from bank two is P * 12 / 100. Total interest is the sum of these two amounts. Because P is the same for both banks, the total interest becomes a single expression in terms of P. Setting this total equal to 1500 rupees yields a simple equation that can be solved for P.

Step-by-Step Solution:
Let the amount invested in each bank be P rupees.Simple interest from the first bank at 8 percent for one year is I1 = P * 8 / 100 = 0.08P.Simple interest from the second bank at 12 percent for one year is I2 = P * 12 / 100 = 0.12P.Total interest from both banks in one year is I1 + I2 = 0.08P + 0.12P = 0.20P.The question states that this total is 1500 rupees, so 0.20P = 1500.Solve for P by dividing both sides by 0.20: P = 1500 / 0.20.Compute 1500 / 0.20 = 1500 * 5 = 7500 rupees.Therefore, Srinivasan invests Rs. 7,500 in each bank.

Verification / Alternative check:
Check interest on Rs. 7500 at 8 percent for one year: I1 = 7500 * 8 / 100 = 600 rupees. Check interest on Rs. 7500 at 12 percent for one year: I2 = 7500 * 12 / 100 = 900 rupees. Total interest is 600 + 900 = 1500 rupees, which matches the given total. Hence, the amount per bank is correctly found as 7500 rupees.

Why Other Options Are Wrong:
If Rs. 5800 were invested in each bank, total interest would be 5800 * 0.08 + 5800 * 0.12, which equals 1160 rupees, less than 1500.
Rs. 15,000 in each bank would produce double the correct total interest.
Rs. 17,000 or Rs. 6,000 would also generate totals that do not equal 1500 rupees. Only Rs. 7,500 in each bank matches the required total interest.

Common Pitfalls:
Some learners mistakenly assume the total interest is computed on a single principal at an average rate instead of summing the two interests. Others forget that the amount is the same in both banks and introduce two different variables unnecessarily, complicating the equation. Keeping the model simple, with one variable for the equal principals, makes the algebra direct and clear.

Final Answer:
The sum invested in each bank by Srinivasan is Rs. 7,500.