'Breaking it Down' Strategy for Teaching Subtraction

By tstyles

There are many ways to teach subtraction to young elementary students that do not require the memorization of an algorithm. This example uses a strategy of breaking the math problem down in ways students can more easily grasp, based on the fundamentals they already know.

Math tools Subtraction can be taught to elementary students by introducing them to number relationships and strategies rather than focusing exclusively on procedures and steps that can be confusing and limiting. The algorithm, though useful in its own way, should not be viewed or taught as a means to an end whenever a difference between two numbers needs to be obtained.

Students first need to understand what the numbers mean, how they relate to one another, and how they can use this information to calculate.

In a previous article about elementary math, I reviewed one strategy for subtracting numbers by "adding up," in which children use addition to find the answer to a subtraction problem. In this article a strategy called "breaking it down" will be reviewed.

Breaking it Down: Example Problem

If the problem, as with the last article, is 1,278 - 580, one doesn't need to set it up in columns and use borrowing to calculate. Nor should a student feel powerless to solve this problem if he or she doesn't know the algorithmic procedure for doing so.

Let's start by breaking down 580 into pieces, such that each piece can be mentally subtracted from the starting number.

  1. First let's subtract 1,278 - 200. This leaves us with a difference of 1,078 with 380 left to subtract.
  2. Let's next subtract 80 from this remaining difference. This leaves us with 998.
  3. Now, we have only 300 left to subtract from 998. Of course, children will need to have a deep understanding of place value to easily subtract 998 - 300, but these math lesson plans on subtraction build this understanding.
  4. 998 - 300 is quite simply calculated as 698, which is the answer to the problem.

If children see that they can break down the number being subtracted into small numbers that can mentally be subtracted, then subtraction becomes a breeze, and even fun!

Innovative Math Teaching

It is said that in teaching algorithms to young children, teachers actually stifle their understanding, creativity, and enjoyment of mathematics, and one can see why from this lesson alone. When math is viewed in such narrow terms as with the algorithm being the defining method for operating on numbers, much is lost in what children can learn.

Teachers should know and follow what the amazing teachers at the Fredudenthal Institute in the Netherlands and the Math in the City teachers in New York City are doing to teach mathematics in order to spearhead the movement into more creative mathematics instruction.