A partner withdraws Rs 1,000 at the beginning of every month. Interest on drawings is 5 per cent per annum. The interest is:

1. Total drawings for the year are Rs 1,000 multiplied by twelve months, which is Rs 12,000. 2. Because a fixed sum is withdrawn at a fixed interval, the average period method applies. 3. For withdrawals at the beginning of every month the average period is 6.5 months. 4. Interest equals total drawings times the rate times the average period over twelve, that is Rs 12,000 times 5 per cent times 6.5 divided by 12. 5. That gives Rs 325. 6. Options B and C are the same computation with the middle-of-month and end-of-month factors of 6 and 5.5, which is exactly the confusion the three monthly cases invite. _Source: TN HSC Class 12 Accountancy (Samacheer Kalvi, Govt of Tamil Nadu), Unit 3 "Accounts of Partnership Firms - Fundamentals", Illustration 16_