An easy way to estimate the sum of two numbers is to round each number and then add the rounded numbers. 
Custom Search
Other Math Activities:Math Reference Library Home Page 

Steps to estimate: 1. Round the numbers to be added, to the greatest place. 2. Add the rounded numbers. It may not be the exact sum, but may be close enough. Example: Estimate 320 + 195. When rounded to the nearest hundreds, 320 rounds to 300,
and 195 rounds to 200. Now, add the rounded numbers. The estimated sum of 320 and 195 is 500. 

Copyright © 19982012 Kidport 