Using Context to Help Students Subtract Whole Numbers
Subtraction should not be nurtured in the context of teaching the algorithm to young children. The algorithm is a complex procedure that, when focused on as a solitary approach, can limit a student's imagination and undermine what should be every teacher's goal of helping children understand the vibrance and living world of mathematics. Instead, teachers should devote their time to teaching children about number and operational relationships that will give children a chance to appreciate mathematics and solve with efficiency and elegance.
Whereas subtraction is concerned I suggest that children can obtain the difference between two numbers by "adding up" or by "breaking down." In this article I illustrate how thinking of number contexts can help children solve math problems easily.
Context and Relevance
As an example, for the number 1,278 - 580, children should be taught to use a context as follows:
- Forget about lining the numbers up nice and neatly.
- Let them make a poster illustrating how to take this problem apart.
- Let's pretend the larger number represents how many Wii games are stocked in a given store. Or perhaps how many gumballs are in a gumball machine. By teaching children to use a meaningful context for their problems, they will more clearly see the answer they seek.
- Now, they must imagine that, of the 1,278 Wii games in stock, 580 have sold in a week's time. How many Wii games are left on the shelf?
- Or they could imagine that in a week's time 580 gumballs were retrieved from the machine in a week's time.
- What if they imagined 1,278 seats in a basketball game and 580 were taken? How can you next find out how many seats are left?
The difference between the contexts given above and a context one might stumble upon in a math textbook is one of relevance.
Teachers need to strive to teach children subtraction in a context that is personally meaningful to the children in front of them. That context may vary depending on the group and their interests.
Most traditional books don't have teachers illustrating subtraction in a context. They often provide contrived examples of subtraction in a meaningless word problem or two, but when a context is actually developed and tailored by the teacher for a specific group to use as a strategy then it may help them better figure the answer to the problem. By seeing numbers in a context children can automatically work out strategies on their own to solve. In using an algorithm that has them only looking at numbers, children may not fully understand the relevance of the computation.
Children should get into the habit of looking at a subtraction problem, any subtraction problem, as a situation, not a string of numbers without meaning. This means nothing to them, and as with everything that means nothing to them, children are left wondering why they are bothering.