When the date of a drawing is not given, the textbook computes interest for an average period of:

1. Interest on drawings depends on how long the money stayed withdrawn, which needs a date. 2. Where the question gives only a total withdrawn during the year with no dates, the book adopts a convention. 3. It computes interest for an average period of six months, stating this explicitly in the relevant illustration. 4. The same convention appears for additional capital introduced without a date, where interest on capital is likewise taken for six months. 5. So a drawing of a stated total, undated, attracts interest on half a year. _Source: TN HSC Class 12 Accountancy (Samacheer Kalvi, Govt of Tamil Nadu), Unit 3 "Accounts of Partnership Firms - Fundamentals", §3.7.3 and Illustration 14_