What is 812.4 rounded to the nearest whole number?

Answer 1

The front end estimate is 800. 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 812.4 to 1 trillion, I would estimate it as 0.
If I had to add 812.4 to 0.0000000001, I would use the number as given, or possibly the front end estimate. If I had to divide it by 8 I would estimate it as 808, because 808/8 = 101. If I had to divide it by 10, I would estimate it as 810, because 810/10 = 81.

Answer 2

812