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Finding Sums with Mental Math

Finding Sums with Mental Math There are a variety of methods that can allow students to add two numbers, or addends, without using pencil and paper. Three methods discussed in our video include “make ten,” “add on,” and “compensation.” The “make ten” approach relies on the associative property of addition. The idea is to re-write one of the numbers (one of the addends) as two smaller numbers. One of these smaller numbers then gets added to the other addend to make a convenient new number. For example, to find the sum of 4,928 and 2,480, the make ten approach allows students to first re-write 4,928 as (4,408 + 520), so that when the 520 is added to 2,480, it results in 3,000. Thus, our sum is 4,408 + 3,000 = 7,408. The “add on” approach relies on the commutative property of addition and allows students to start with either of the two terms they are adding. For example, to find the sum of 4,928 and 2,480, the add on approach allows students to first add 80 onto the first addend, 4,928 + 80 = 5,008. Then, they add 400 onto the running total of 5,008 to get 5,408. Finally, they add 2,000 onto the running total to get 7,408. This approach reinforces place value as students add tens, hundreds, and thousands to the first number. The “compensation” approach allows students to add a convenient number to one addend, and take it away from the other, to compensate for the addition. For example, when finding the sum of 4,928 and 2,480, a convenient number to add onto the first number is 72, since it would result in 5,000, an easy number to work with mentally. Thus, we subtract 72 from 2,480 to compensate, and get 2,408. Finally, we add our addends to get the sum: 5,000 + 2,408 = 7,408. See our related videos on the associative property of addition:    • Associative Property of Addition   and on the commutative property of addition:    • Commutative Property of Addition   Finding sums with mental math is part of the Common Core Standards for Grade 2. https://www.state.nj.us/education/ccc... Math Videos for Parents Follow us on Facebook: www.facebook.com/mathvideosforparents Subscribe to our YouTube Channel:    / @mathvideosforparents1706   Please reach out with any problem requests. We enjoy helping you so that you can help your kids!