Let the total work be \( W \).
Work done per day by 12 men: \[ 12 \times \frac{W}{64} = \frac{12W}{64} = \frac{3W}{16} \]
Work done per day by 5 women: \[ 5 \times \frac{W}{80} = \frac{5W}{80} = \frac{W}{16} \]
Total work done per day: \[ \frac{3W}{16} + \frac{W}{16} = \frac{4W}{16} = \frac{W}{4} \]
Days required to complete \( W \) work:
\[ \frac{W}{W/4} = 4 \text{ days} \]
Thus, the correct answer is 4 days (Option C).
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?