Common Core Help – Taking Apart Hundreds

January 11th, 2015 by Math Tricks | No Comments | Filed in Common Core Help

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Help With Common Core Homework

I have started a new feature here to provide help with common core math.  The methods taught to students are very different today – much more so than just a few years ago.  It is my hope that this will help the parents out there who are struggling with their kids homework.  I know how difficult it seems at first glance, but with a little bit of instruction, you can see how the work is done.

My son came home with an advanced 2nd grade homework assignment the other day, and he asked me to help him with it.  “No problem”, was my response as I held out my hand to grab the bundle.  I looked down at the first problem:

835 – 98

I looked at my son and chuckled.  “You know how to do this”, I said nodding my head.  “No, looked at the instructions”, he whined.  Above the problem set was written:

Take apart hundreds to subtract

I stared at the words, and then at the problem.  How do you take apart hundreds?  Hmmm . . . At this point, I was wondering if my son was loosing faith with his “math expert” dad.  Well, after a little searching, I found a description of the method, which is really a clever way to perform mental arithmetic:

1: Take apart 835 as 735 and 100

2: Subtract 98 from 100

Pretty easy, eh?  I did not know what to do just given the “Take apart hundreds to subtract” instruction, and this is where a lot of people get frustrated.  Well, anyways, here are a few more examples from my son’s homework page:

748 – 97

648   100

100 – 97 = 3

648 + 3 = 651

748 – 97 = 651

395 – 99

295   100

100 – 99 = 1

295 + 1 = 296

395 – 99 = 296

600 – 97

500   100

100 – 97 = 3

500 + 3 = 503

600 – 97 = 503