## Friday, March 04, 2016

### Another example of a parent showing how little they understand basic arithmetic concepts (aka: this isn't an example of Common Core being wrong)

I saw another example of complaining about the mathematics Common Core by a parent whose grasp on mathematics wasn't as strong as they thought it was:

The "brilliant" commentary from the page is: "Imagine how confused this kid is now when teachers are telling him "Yes, you can get 10 when you add 8+5." It's almost like we are intentionally and structurally trying to make kids less intelligent, or something ..."

*SIGH*

This person apparently doesn't even know how much they are demonstrating their lack of understanding about the mathematics they are complaining about. Indeed, they fail to even note that the point they think the teacher is making ("Yes, you can get 10 when you add 8+5") is not what the teacher is actually saying. Indeed, if the parent actually read the entirety of the explanation written in blue marker, they would have seen, "Yes you can. Take 2 from 5 and add it to 8 (8+2=1). Then add 3." (Emphasis mine.) The whole bloody point is that you can get 10 from 8+5, so long as you also understand that you will have an additional 3, because:

8+5 = 10+3

Duh!

I will admit that it's a really poorly worded question. However, the official answer is actually correct, and - more importantly - it shows the application of the distributive property in arithmetic, which is a principle so foundational in mathematics that - without it - mathematics wouldn't function.

To describe why 8+5 = 10+3 you have to recognize that:

8 = 1+1+1+1+1+1+1+1+1 and 5 = 1+1+1+1+1

therefore

8+5 = 1+1+1+1+1+1+1+1+1+1+1+1+1

And this can be re-grouped in any way you want (and those ways go on into infinity if you consider configurations that include negative and non-integer numbers), because of the distributive property. One of those infinite number of ways is 10+3.