एक निश्चित राशि पर 12% प्रति वर्ष की दर से 2 वर्ष का चक्रवृद्धि ब्याज ₹1,590 है। उसी राशि पर दोगुने समय और आधी वार्षिक ब्याज दर पर साधारण ब्याज कितना होगा?

A retail bank issues a 'Green Fixed Deposit' scheme for a 3-year tenure. The bank offers an interest rate of 7.5% p.a. compounded annually. A customer invests 5,00,000 INR. Simultaneously, the bank allocates these funds to a 'Rooftop Solar Project' under a priority sector loan at 10.5% p.a. (simple interest) for the same duration. Calculate the bank's 'Gross Spread' (the difference between total interest earned from the loan and total interest paid to the depositor) over the entire 3-year period.

The ratio of compound interest (compounded annually) to simple interest on a retirement annuity after 2 years at the same annual rate of interest is 23 : 20. What is the annual rate of interest?