I'm trying to understand common core, however it seems who ever is making up these

 

equations is using arbitrary numbers to make their point. I could understand if the numbers were

 

derived from the question, but that's not the case. Example:

 

_______________________________________________________________

 

What does 26 + 17 =?

 

1.) First think: 4 + 13 = 17 ( why not use 16 + 1 or 12 + 5...why 14 + 3)

 

2.) Add 26 + 4 = 30

 

3.) Add 13 + 30 = 43

 

________________________________________________________________

 

~ee

I'm trying to understand common core, however it seems who ever is making up these

 

equations is using arbitrary numbers to make their point. I could understand if the numbers were

 

derived from the question, but that's not the case. Example:

 

_______________________________________________________________

 

What does 26 + 17 =?

 

1.) First think: 4 + 13 = 17 ( why not use 16 + 1 or 12 + 5...why 14 + 3)

 

2.) Add 26 + 4 = 30

 

3.) Add 13 + 30 = 43

 

________________________________________________________________

 

~ee

What they're doing is

 

26 + 17 =?

 

26 rounded to the next 10 is 30.

 

30 - 26 = 4

 

17 - 4 = 13

 

26 + 4 = 30

 

30 + 13 = 43

gotcha, thanks!

I'm not familiar with the term "common core"; is either of these preferred?

 

26 + 17 = (26 - 3) + (17 + 3) = 23 + 20 = 43

 

26 + 17 = (26 + 4) + (17 - 4) = 30 + 13 = 43