Now, The Three-Digit Mental Addition

Dear readers,

The strategy for adding three-digit numbers mentally is the same as adding two-digit numbers.  Please refer to my previous post regarding two-digit left to right mental addition to understand this three-digit addition better.

As the two-digit mental addition, we need to simplify our problem by breaking it into smaller and more manageable parts.  Let’s us try the following :

    427                                                                                                                   +  218  ( 200 + 10 + 8 )

Starting with 427, we add 200, then we add 10, and lastly add 8.  After adding 200 (ie 427 + 200 = 627), our problem becomes 627 + 18.  And after adding 10 (627 + 10 = 637), our problem simplifies to 637 + 8 = 645.  This thought process can be illustrated as follows :

427   +   218        =       627   +   18        =        637   +   8         =       645               

                  ( first add 200)             (then add 10)             (lastly add 8)      

The objective is to keep simplifying the problem until we are just  adding a one-digit number.  All mental addition problems can be done by this method.                  

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Posted on May 25, 2009, in Info Matematik. Bookmark the permalink. Leave a comment.

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