My explanation in Teaching Subtraction

Hi Parents!!!!


What is Mr Thurlow trying to do in Maths, in Subtraction? Here is my explanation

1. I want the students to subtract knowing the actual value of the number i.e. Hundreds, Tens and Ones. With the vertical method that you as parents (and I) were taught to do subtraction, we knew it worked but did not necessarily understand the actual value of the number we were subtracting at age 8 and 9. This is the reason why I teach the students to solve subtraction problems using the alternative "Numeracy method" as demonstrated above.
   

1. I have taught the Numeracy method using the example of a bus traveling to a destination (the answer) as above.


2. Using the number line gives a visual for the students (they may not need this later on).


3. From the above example, my first bus stop is to get rid of the hundreds place value (893-100=793).


4. There are a number of bus stops to get rid of the tens place value. The reasoning is that students become confused when subtracting below a particular rounded 100 number - example 933, 923, 913, 903, 893..... the confusion may occur when subtracting below 900 (i.e. from 903 - 893) in this example.

This is why I ask my students to subtract the tens place value in individual 10's.
Further on in their schooling, students may not need to subtract in individual 10's for the ten place value. They may subtract in 20's or 50's as well.

Above picture example 783 ,773 ,763 (Here are the bus stops for the 10's place value)

5. Finally the bus stops once to get rid of the one place value. For the example above I have used two bus stops, as it easier, to take away 3 then another 2. 763 - 3 =760 then 760-2 = 758

Finally we are at the answer (destination) = 758


There is nothing wrong in the vertical method of subtraction that we learned. However, I ask you to consider does your child understand the true value of the numbers being subtracted when using this method?