Hey, this is Jenny,  this is how you estimate products:

1.Round each number to the greatest place.

789 x 456 ~ 800 x 500

2.Find the basic math fact in the rounded numbers then multiply them.  

8 x 5 = 40

3.Count the zeros and add the total number of zeros behind the basic math fact. 

800 x 500 = 40-0,000

                                                                                         1,2,  3,4       1,2,3,4,

4.Multiply the unrounded numbers and see if they are close to the rounded numbers. If not,

 something went wrong, but don't give up! Just try again!        789 x 456 = 350,784

                            This is how you get the answer to: 789 x 456 by estimating the product!!