How do you estimate 3916?

Answer 1

The front end estimate is 4000. But estimating a single number, in isolation and without context, is a complete waste of time. It all comes down to the context of what needs to be done with the number.

If I had to add 3916 to 1 trillion, I would estimate it as 0.
If I had to add 3916 to 0.0000000001, I would use the number as given, or possibly the front end estimate. If I had to divide it by 39, I would estimate it as 3939, because 3939/39 = 101. If I had to divide it by 10, I would estimate it as 3920, because 3920/10 = 392.

Answer 2

To the nearest hundred, 3900