Ram's capital has two components with different time periods:
Initial Capital: Rs. 1,20,000 (from 1st Jan 2020 to 31st Dec 2020)
Time period = 12 months
Interest = Principal×Rate×12Time
Interest on initial capital = 1,20,000×10015×1212 = Rs. 18,000
Additional Capital: Rs. 50,000 (from 1st July 2020 to 31st Dec 2020)
Time period = 6 months (July to December)
Interest on additional capital = 50,000×10015×126 = Rs. 3,750
Total Interest on Ram's Capital = 18,000 + 3,750 = Rs. 21,750
The additional capital introduced mid-year earns interest only for the remaining 6 months of the accounting period, which is why it's calculated separately from the initial capital that remained invested for the full year.