To solve this problem, let’s analyze the information given and calculate accordingly.

1. Dev's Efficiency: Dev completes the project in 20 days, so his work rate is: $\text{Work rate of Dev} = \frac{1 \text{ project}}{20 \text{ days}} = \frac{1}{20} \text{ projects per day}$

2. Arun's Efficiency: Arun is 25% more efficient than Dev. This means Arun's work rate is 25% higher than Dev's: $\text{Work rate of Arun} = 1.25 \times \frac{1}{20} = \frac{1.25}{20} = \frac{5}{80} = \frac{1}{16} \text{ projects per day}$

3. Arun's Time to Complete the Project: Since Arun works at a rate of $\frac{1}{16}$ projects per day, the time he will take to complete one project is: $\text{Time for Arun} = \frac{1 \text{ project}}{\frac{1}{16} \text{ projects per day}} = 16 \text{ days}$

Answer: Arun will take 16 days to complete the same work.

Would you like more details or have any questions?

Additional Related Questions:

1. If Arun were 50% more efficient than Dev, how many days would he take?
2. What would be the completion time if both Dev and Arun worked together?
3. How much more efficient would Arun need to be to finish the project in 10 days?
4. If Dev worked for 10 days and Arun took over afterward, how long would Arun need to finish?
5. If another person is 10% less efficient than Dev, how long would they take?

Tip: When solving efficiency problems, remember that higher efficiency (or work rate) results in a lower time required to complete the task.