Final answer:
3999.671 should be added to 0.329.
Step-by-step explanation:
To find out what should be added to 0.329 to get 4,000, we can subtract 0.329 from 4,000.
4,000 - 0.329 = 3999.671
Therefore, the number that should be added to 0.329 to get 4,000 is 3999.671.