Vishnu and Mishu are partners in a firm. Mishu draws a fixed amount at the end of every quarter. Interest on drawings is charged @ 15\% p.a. At the end of the year, interest on Mishu's drawings amounted to \rupee9,000. Interest on drawings was charged on drawings of Mishu for:
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For periodic drawings, calculate the average period using:
\[
\text{Average period} = \frac{\text{Sum of months remaining}}{\text{Number of intervals}}.
\]
Adjust the formula based on whether the drawings are made at the beginning or end of the interval.
For fixed quarterly drawings made at the end of each quarter, the average period for interest calculation is:
\[
\text{Average period} = \frac{(9 + 6 + 3 + 0)}{4} \text{ months} = 4.5 \text{ months}.
\]
Thus, the interest is charged for an average of 4 \(\frac{1}{2}\) months.