WALT: multiply 3-digits by 1-digit (Extension: 2 digits by 2 digits)
Today we are going to ensure understanding of the column multiplication method, which means continuing what we were doing yesterday. As there are only a small number of steps, it is important to understand how and why each of them are done, which you will find both from what is on the website and also what is on the video.
There are some misconceptions, or misunderstandings, that can be made using this method. The main one is usually transposing the numbers, so the number carried to the next place value column is confused with the number placed underneath the line. Also, sometimes people forget to carry numbers to the next column, so if you are making these errors, do not worry as that is quite normal.
Today's task is to attempt the next challenge up from the one you tried yesterday. If you were not too successful yesterday when checking your answers, it is more than fine to re-try the sums you tried yesterday to see if you have understood it more today. Do not be afraid to re-read the guidance or re-watch the video.
I have also set 3 tasks on https://login.mymaths.co.uk/login# related to multiplication. They are differentiated so please try the task with which you feel most comfortable. You only need to do 1 task however you can obviously try more if you would like to.
The instructions from yesterday have been re-entered below and the video is also on here again, along with another video explaining how to multiply 2-digits by 2-digits for those who would like to try the extension task.
I have made videos explaining the method however they are too large to post on here. The link for the video, explaining multiplying 2-digits by 1-digit can be found on this link: https://youtu.be/2fnlze9rRqo and the link for the video explaining multiplying 2-digits by 2-digits is: https://youtu.be/cF44zs2mgqM
We will first multiply 43 x 2 using this method. This does not require any carrying or exchanging of numbers so is the most straight-forward multiplication sum.
Remember how we always ensure we start by using our place value columns, so we will write the sum like this:
H T O
Step 1: Multiply the numbers in the 'ones' column together, so here we multiply 3 x 2, which equals 6. The answer remains in the 'ones' column, underneath the line.
Step 2: Multiply the number in the 'tens' column by the bottom number, making our sum, 4 x 2. The answer to this sum is '8' and this is placed in the 'tens' column, underneath the line, making the answer '86'.
The sum for Step 2 is actually really 40 x 2 as the '4' is in the tens column however you do not need to do anything with this, other than know the '4' is in the 'tens' column.
We will multiply 76 x 3 using this method. This requires carrying of numbers so is a little more difficult to calculate however as long as you know your 3 times tables, you will be able to work it out.
Once again, remember we always ensure we start by using our place value columns, so we will write the sum like this:
H T O
2 2 8
Step 1: Multiply the numbers in the 'ones' column together, so here we multiply 6 x 3, which equals 18. The 'ones' number in 18, which is '8', goes into the 'ones' column underneath the line. However there is still 1 'ten' that we need to put into our sum. We need to put this in the 'tens' column, above the line, as we will use it a little later in our sum.
Step 2: Multiply the number in the 'tens' column by the bottom number, making our sum, 7 x 3. The answer to this sum is '21' so the '1' would be placed in the 'tens' column, however we have to add the small number '1' that we put above the line. This mean we add 1 + 1, which equals '2' and place this underneath the line in the 'tens' column.
This is why it is imperative that the numbers are lined up properly. This then results in the '2' being placed in the 'hundreds' column, resulting in the answer being '228'.
You can always use the expanded method to check your answer.