Given information:
- Length of the field = 25 cm
- Breadth of the field = 19 cm
- The boy completes 3 rounds in 5.9 hours.

To find:
- How many times will the boy complete 10 rounds?

Explanation:

1. Calculate the distance covered in 1 round:
- The distance covered in 1 round is equal to the perimeter of the field.
- Perimeter of a rectangle = 2(length + breadth)
- Perimeter of the field = 2(25 cm + 19 cm)
- Perimeter of the field = 2(44 cm)
- Perimeter of the field = 88 cm

2. Calculate the time taken to complete 1 round:
- The time taken to complete 1 round is given as 5.9 hours.
- Therefore, the time taken to complete 1 round = 5.9 hours

3. Calculate the time taken to complete 10 rounds:
- To find the time taken to complete 10 rounds, we can multiply the time taken to complete 1 round by 10.
- Time taken to complete 10 rounds = 5.9 hours × 10
- Time taken to complete 10 rounds = 59 hours

4. Calculate the number of times the boy can complete 10 rounds:
- To find the number of times the boy can complete 10 rounds, we can divide the total time taken to complete 10 rounds by the time taken to complete 1 round.
- Number of times to complete 10 rounds = Total time taken to complete 10 rounds ÷ Time taken to complete 1 round
- Number of times to complete 10 rounds = 59 hours ÷ 5.9 hours
- Number of times to complete 10 rounds = 10

Conclusion:
The boy will be able to complete 10 rounds 10 times.