Answer:
Use the value the problem statement tells you. Otherwise, use a better approximation.
Explanation:
π ≈ 3.141592653589793238... (a non-repeating infinite decimal)
3.14 = 3.14
22/7 = 3.142857142857_142857
355/113 = 3.14159292035... (a very long repeating decimal)
You can see that the third decimal place is wrong in both of your approximations. The last approximation shown has 7 good decimal digits. A good scientific or graphing calculator will have an internal value for pi that is good to 10 or 12 digits or more (preferably, at least 32 digits).
You should use a value for pi that has at least one more digit of accuracy than the number of significant digits in your answer.