PS/IS 686 | Brooklyn, NY

Grade 4 Math: Addition and Subtraction Strategies: To Algorithm or Not to Algorithm

October 13, 2017

Dear Familes,

Fourth graders have been reviewing their addition and subtraction strategies  It has been wonderful to see the flexible strategies they are bringing with them.  They are quite adept at decomposing (splitting) numbers into place values.  

Many of them are also transforming the problem into an easier problem.  For example, given 3004 – 581, they can turn it into 2999-586.  Subtracting across zeroes often leads to numerous mistakes, and this transformation makes the problem a simple subtraction situation.

Flexibility with strategies is really important.  It requires looking at the number to determine which strategy suits the numbers.  This shows true number sense.  This is why standard algorithms aren’t required until 4th grade.  When students are taught algorithms too early, they tend to blindly apply them rather than look at the numbers.  Then we have students (and many adults of my generation) that see 1001 – 999 and begin to cross out and regroup.  Flexibility with numbers will allow a student to look at the numbers and realize that they are only 2 apart, so it’s a simple problem.  While it is important to know algorithms, they should just be another strategy we have in our toolbox.  

Next week, as was posted on School Loop, we will be having our first math test of 4th grade.  It will be on addition and subtraction (including the algorithms), estimation, and vocabulary.  The test will most likely be on Tuesday or Wednesday. I will update on School Loop when it is definite.

Have a great weekend!