Multiplication

Well! It is official! Your student can officially multiply 4 digit numbers by 1 digit numbers.  In other words, if I tell a student to multiply 4,357 by 5, they can do it!  I know that students were worried about learning this skill, but when I taught them the two methods that we learned this past week, they grasped the skill  quite quickly and rocked it! Below is a more in-depth look at the two methods I taught this last week.

Please remember, we are only multiplying by single digit numbers so far!

The Partial Products Method: 

The partial products method is a building block to understanding the standard algorithm (or the way we learned how to multiply).  Say, for example, I have the problem 475 X 3.  I would think of it as 3 X 5 = 15, 3 X 70 = 210, and 3 X 400 = 1,200.  Now, I need to add those up, so the answer would be 1,425.

A lot of students love this method, however, it is not always the most efficient way to multiply, so we also learned standard algorithm.


The Standard Algorithm:

Now, this may not be fully the way that you and I learned to multiply, but it is VERY close.  Let's use the same numbers, 475 X 3.  Students would look at this problem and go through the following though process:  3 X 5 is 15, so I put 5 down in ones place.  Now, I have 3 X 7, but plus 1 (from that 15), so I have 22.  So, I put the 2 down in the tens place.  Now, I have 3 X 4, but plus 2 (from that 22), and so I have 14, so I write that down.  This means my total number is 1,425.

Here is a video, but please remember that students are not writing the "carry" numbers above, they are writing the "carry" numbers on the answer line.

Math Video


It is very important that students memorize their multiplication facts.  I do know that they sell math flash cards at Dollar General, Dollar Tree, and at other stores.  I have found that students know the concept of multiplication, but what is holding them back is the actual knowledge of their facts.  Please keep working with your students on these.