Скачать или смотреть Subtraction-fest 08 ~ Mental Subtraction By Counting

This video is the first of three in which I describe common mental subtraction methods. The subtraction methods that we use on paper are, generally, too cumbersome for mental calculation. Also, we rarely subtract large numbers mentally ... so we use different techniques in this case ... ones that don't require remembering lots of detail!

Because we count quite naturally by ones, tens and hundreds, the first method uses this simple skill to find the difference between numbers.

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RATIONALE FOR THIS SERIES

Some of you have expressed quite some interest in different subtraction methods/algorithms. This resulted from my posting two lengthy videos in which I explained WHY different algorithms worked.

It became apparent, however, that I needed to create a series of much shorter videos in order to DEMONSTRATE these methods (and more) without the lengthy explanations in those first two videos.