Access full lesson containing this video at: http://www.yourteacher.com/prealgebra/estimatingsumsanddifferences.php Students learn to estimate a sum or difference by first rounding each number to the place specified in the problem. For example, to estimate 4,909 + 3,217 by rounding each number to the nearest thousand, first round 4,909 up to 5,000, and round 3,217 down to 3,000, then add 5,000 + 3,000 to get 8,000. Less