Lesson video

Hello there.

My name is Mr. Goldie and welcome to today's math lesson.

And here is our learning outcome.

I can use column subtraction to subtract from a two or three-digit number.

And here are the keywords.

I'm going to say each keyword.

Can you say it back? The first keyword is minuend.

The next keyword is subtrahend.

And the next keywords are column subtraction.

Let's take a look at what those words mean.

So the minuend is the number being subtracted from.

A subtrahend is a number subtracted from another.

And column subtraction is a way of subtracting numbers by writing a number below another.

And here is our lesson outline.

So the first part of the lesson, we're going to be looking at column subtraction with two-digit numbers.

And in the second part of the lesson, we're going to be looking at column subtraction with three-digit numbers.

Let's get started.

In this lesson you will meet Sam and Aisha.

And Sam and Aisha are going to be helping you with your math and asking you some tricky questions.

Sam uses base 10 blocks to represent the calculation 57-23.

"I start with 57," says Sam.

So here's 57 represented using base 10 blocks.

When we use base 10 blocks for subtraction, we only make the minuend.

And so it's a little bit different to when you use base 10 box for addition.

When you use it for addition, you make both addends, but for subtraction you only make the minuend and then you subtract the subtrahend from it.

"First, I subtract 3 ones," says Sam.

So Sam subtracts 3 ones.

"Then I subtract 2 tens." So Sam has subtracted 2 tens.

"57 - 23 = 34," says Aisha.

And you can see there the three different parts of the subtraction calculation.

The minuend is all of it.

The subtrahend is the part that's now faint, the part we subtracted.

And the difference is the part that is left.

Sam and Aisha use base 10 blocks to help them represent 57-23 as a column subtraction.

"I start with 57," says Sam.

Here's 57, represent with base 10 blocks.

And remember if you're using base 10 blocks to represent subtraction, you only make the minuend.

"The minuend always appears first in a column subtraction.

The subtrahend is written underneath," says Aisha.

So here is 57 - 23, written as a column subtraction.

It's really important those ones and tens digits line up with each other.

"First, I subtract 3 ones," says Sam.

So Sam subtract 3 ones from the base 10 blocks.

"7 ones subtract 3 ones is equal to 4 ones," says Aisha.

So Aisha writes 4 ones in the ones column.

"Then I subtract 2 tens," says Sam.

So Sam subtracts 2 tens from the base 10 blocks.

"5 tens subtract 2 tens is equal to 3 tens," says Aisha.

So Aisha writes 3 tens.

And Aisha writes out 3 tens as part of the difference and is written underneath the subtrahend and the minuend.

"57 - 23 = 34," says Sam.

Sam and Aisha used base 10 blocks to help them represent 66 - 42 as a column subtraction.

So Sam says, "I start with 66." So Sam represents 66 using base 10 blocks.

And Aisha just reminds us how to write a column subtraction.

So she says, "The minuend always appears first in a column subtraction and the subtrahend is written underneath." So here is 66 - 42, written as a column subtraction.

And remember it's really important to line up those ones and those tens so that they are in the right columns.

"First, I subtract 2 ones," says Sam.

So Sam subtracts 2 ones.

"6 ones subtract 2 ones is equal to 4 ones," says Aisha.

"Then I subtract 4 tens," says Sam.

So Sam subtracts 4 tens.

Aisha says, "6 tens subtract 4 tens is equal to 2 tens." And 2 tens is the tens number of the difference, and that of course is written underneath the minuend and the subtrahend.

"66 - 42 = 24," says Sam.

Aisha and Sam represent 76 - 25 as a column subtraction.

So here is 76 - 25 as a column subtraction.

So this time, Sam isn't going to use base 10 blocks to help him represent the number.

So Sam has stopped using base 10 blocks to represent the numbers.

It doesn't mean that you have to, so if you still find it helpful, you might want to do that.

So we start with the numbers with the smallest place value first.

So which numbers have got the smallest place value? So in a two-digit number like this, we would start with the ones number.

6 ones subtract 5 ones is equal to 1 one.

And then 7 tens subtract 2 tens is equal to 5 tens.

Sam says, "76 - 25 is = 51." Aisha and Sam represent 43 - 20 as a column subtraction.

We start with the numbers with the smallest place value first.

That's really important.

We always start with the numbers with the smallest place value.

In this case, it's the ones.

There are no ones to subtract so there are still 3 ones left.

So we've got 3 ones subtract 0 ones is equal to 3 ones.

4 tens subtract 2 tens is equal to 2 tens.

"43 - 20 = 23," says Sam.

Now it's your turn to have a go at one.

Use column subtraction to calculate 59 - 13.

So here's how you recite it out.

And Sam's just reminding you, "Start with the numbers with the smallest place value." You might want to use paper and pencil, you might want to use a whiteboard and a whiteboard pen.

Have a go at writing down that calculation and see if you can work out the difference.

Don't forget to start with the numbers with the smallest place value first.

Pause the video, see if you can work out the difference.

And welcome back.

Let's take a look, see if you've got the right answer.

So Aisha says, "9 ones subtract 3 ones is equal to 6 ones.

5 tens subtract 1 ten is equal to 4 tens." 59 - 13 = 46.

So very well done, if you've got 46 as the difference.

Aisha calculates 76 - 52 using column subtraction.

So first of all, Aisha writes down the calculation as a column subtraction, and then she starts off with the numbers with the smallest place value first.

So 6 ones subtract 2 ones is equal to 4 ones.

7 tens subtract 5 tens is equal to 2 tens.

Aisha has worked out the difference, 24.

76 - 52 = 24.

Calculate 47 - 25 using column subtraction.

Tell a friend the steps and if you don't have a friend available, then talk to a cuppy toy.

Pause the video and see if you can work out how you would calculate the answer to 47 - 25 using column subtraction.

And welcome back.

Did you manage to work out the answer? Did you find that difference? Let's take a look.

So first of all, it's important you set out the calculation correctly, so 47 with 25 written underneath it.

One's number of the subtrahend needs to be beneath the one's number of the minuend.

The tens number of the subtrahend needs to be below the tens number of the minuend, really important.

So first of all, start with the numbers with the smallest place value first.

So 7 ones subtract 5 ones is equal to 2 ones.

4 tens subtract 2 tens is equal to 2 tens.

So 47 - 25 = 22.

Very well done, if you've got the right answer.

Very well done if you managed to explain each of the steps to a friend.

And let's move on to look at Task A.

So the first part of Task A, you're going to complete each column subtraction.

So remember, start with the numbers with the smallest place value first.

So for that first one, A, 56 - 34.

First of all, you'd subtract 4 ones from 6 ones, and then you'd subtract 3 tens from 5 tens and work out what the difference is.

Here is the second part of Task A.

So complete each equation using column subtraction.

This time you're given the equation, gotta work out what the difference is.

But also you've gotta set it out like a column subtraction as well.

So look carefully, where's the minuend? That's the number you are subtracting from.

Where's the subtrahend? That's the number you are subtracting.

And where would the difference go? That's the result after subtracting one number for another.

So see if you can complete those column subtractions.

And then finally, Sam, oh, Sam.

Sam has mixed up these column subtractions.

Can you make them correct using the six numbers below? So you've got there six numbers 20, 25, 49, 37, 78 and 83.

Two of those numbers go into each column subtraction to make it correct.

So one of them subtract the other gives you a difference of 24.

One of them subtract the other gives a difference of 63, and one of them subtract the other gives a difference of 41.

So Sam is saying, "Please can you put each minuend and subtrahend into the correct column subtraction?" So look very, very carefully at those numbers and pay particular attention to those ones digits because it's the ones digits that's going to help you a little bit here.

So look really carefully, how would you get a difference of 4? So which two numbers have a difference of 4? And that might give you the first two numbers 4, what number subtract which number equals 24.

So pause the video and have a go and see if you can solve Sam's challenge.

And welcome back.

How did you get on and did you manage to get on to Sam's challenge? Did you manage to solve Sam's challenge? Very well done if you did.

Let's take a look at the answers.

So with the answers for part one of Task A.

So 56 - 34 = 22.

43 - 12 = 31.

So well done if you've got those correct.

Let's move on to part two of Task A.

So for that first calculation we had 73 as the minuend and 61 as the subtrahend and 12 is the difference.

73 - 61 = 12.

And that's how you should have set it out as a column subtraction.

So we start with the minuend, the subtrahend is written underneath and the difference appears underneath the subtrahend.

So well done if you managed to get those correct.

And finally, let's move on to part three, so this was Sam's challenge.

So here are the answers for Sam's challenge.

So that first one, 49 - 25 = 24.

9 - 5 = 4.

So you don't have to look at both digits, you maybe just looked at the ones digit to help you work out the answers.

How did you know you were correct? How could you check? Did you actually try to solve each column subtraction? Did you actually go through its starting with the ones numbers and subtract the subtrahend from the minuend.

Very well done if you got onto part three of Task A and you managed to solve it.

And let's move on to our second part of the lesson.

So the second part of the lesson is column subtraction with three-digit numbers.

Aisha and Sam represent 266 - 125 as a column subtraction.

So the minuend always appears first in a column subtraction, the subtrahend is written underneath.

Here is how you would set out that column subtraction.

We start with the numbers with the smallest place value.

So remember we always start with the numbers with the smallest place value first.

So in this case, be the ones.

6 ones subtract 5 ones is equal to 1 one.

6 tens subtract 2 tens is equal to 4 tens.

2 hundreds subtract 1 hundred is equal to 1 hundred.

So 266 - 125 = 141.

Aisha and Sam represent 367 - 305 as a column subtraction.

We start with the numbers with the smallest place value.

So 7 ones subtract 5 ones is equal to 2 ones.

Remember we always start with the minuend and subtract the subtrahend.

There are no tens to subtract.

So 6 tens subtract 0 tens is still 6 tens.

3 hundreds subtract 3 hundreds is equal to zero.

"We don't really need to write a zero in the hundreds column," says Sam.

So you don't really need to write it there.

Aisha's written it there just to remind herself that she's finished that calculation, that she's completed it.

So 367 - 305 = 62.

You notice there that Sam hasn't written the zero in the hundreds column of 62, it's not needed.

Aisha and Sam represent 379 - 65 as a column subtraction.

And Sam's just reminding us we start with the numbers with the smallest place value.

So we start off with the ones, 9 ones subtract 5 ones is equal to 4 ones.

So we write 4 ones in the correct place.

7 tens subtract 6 tens is equal to 1 ten.

So 1 is the digit written in the tens column.

There are no hundreds to subtract.

We've got 3 hundred subtract no hundreds is equal to 3 hundreds.

So 379 - 65 = 314.

And here is one for you to try on your own.

Represent 485 - 370 as a column subtraction.

Then find the difference.

So how would you work out the difference between those two numbers? How would you set it out as a column subtraction? What number would you start off by subtracting first? This is where you'll need pencil and paper or a whiteboard and whiteboard pen.

Have a go writing out that calculation.

See if you can work out the difference.

Pause the video and have a go at trying to work out the difference between those two numbers using column subtraction.

And welcome back.

Did you manage to work out the difference? Let's find out whether you were right.

So here's how you should have set out the column subtraction with the digits lining up with the ones, tens and a hundreds digits of the subtrahend underneath the ones, tens and a hundreds digits of the minuend.

And Aisha's gonna launch straight in there with "There are no ones to subtract." Remember we start off with the numbers with the smallest place value first.

So there are no ones to subtract, 5 ones subtract 0 ones is equal to 5 ones.

8 tens subtract 7 tens is equal to 1 ten.

So 1 is written in the tens column of the difference.

And 4 hundreds subtract 3 hundreds is equal to 1 hundred.

So 1 is written in the hundreds digits of the difference as well.

485 - 370 equals = 115.

Very well done if you got that as the answer.

Aisha and Sam try to find the missing digits in this column subtraction.

There's a three-digit number being subtracted from a three-digit number, but some of the digits are missing.

How do you work out the missing numbers? Sam says, "We start with the numbers with the smallest place value first." So even when you've got a puzzle like this, we still start off with the numbers with the smallest pace value first of all.

So 8 ones subtract how many ones is equal to 3 ones.

To find a missing part, we have to subtract the other part from the whole.

So 8 in this case is the whole and the 3 is the other part.

So 8 - 3 would be equal to 5.

So the missing number must be 5.

So 8 - 5 = 3.

How many tens subtract 3 tens is equal to 2 tens.

What's the missing number? What's the missing tens digit of the minuend? "To find a missing whole, add the parts together," says Sam.

Very useful advice there Sam.

3 + 2 = 5 When the whole is missing add the parts together.

So 5 tens subtract 3 tens is equal 2 tens.

And that last one, 5 hundreds subtract how many hundreds is equal to 3 hundreds? Well, we should know that one 'cause we've just done a very, very similar calculation, haven't we? So to work out a missing part, subtract the other part from the whole.

5 - 3 = 2.

5 hundreds subtract 2 hundreds is equal to 3 hundreds.

So the missing hundreds digit is a 2.

So with both Sam and Aisha we've worked out the missing digits into that column subtraction.

558 - 235 = 323.

Here's one for you to try on your own.

Find the missing digits in this column subtraction.

So look really carefully, for the minuend the hundredth digit is missing and the ones digit is missing.

For the subtrahend, the tens digit is missing.

And don't forget like always start with the numbers with the smallest place value first.

Pause the video and see if you can work out the missing digits.

And welcome back.

How did you get on? Did you manage to find all three missing digits? Let's take a look to see whether you got them right.

Here's Aisha, Aisha said, "How many ones subtract 0 ones is equal to 3 ones?" Not too difficult that one is there.

The missing number is 3.

So 3 is the missing ones digit.

9 tens subtract how many tens is equal to 3 tens.

So remember when there's a missing part, subtract the other part from the whole.

9 - 3 = 6.

So 9 - 6 must be equal to 3.

So 9 tens subtract 6 tens is equal to 3 tens.

So the missing tens digit is a 6.

And then finally, the missing hundreds digit of the minuend.

How many hundreds subtract 2 hundreds is equal to 2 hundreds.

And again, not too difficult that one, is it.

So when the whole is missing add the parts together.

4 hundreds subtract 2 hundreds is equal to 2 hundreds.

Very well done if you manage to work out all three missing digits, that's fantastic.

And then here's Sam.

And Sam says 493 - 260 = 233.

And here is Task B.

The first part of Task B, complete each column subtraction.

There is a three-digit number, subtract a three-digit number.

Can you work out the difference? So don't forget to start with the numbers with the smallest place value first.

Here's part two of Task B.

So complete each equation using column subtraction.

So you've been given the equation, you've gotta complete that column subtraction.

Work out the difference, and then complete the equation afterwards.

Which number is the minuend or which number is the subtrahend? And where would you write them on the column subtraction.

And finally, part three.

Find the missing digits in each column subtraction.

This is the kind of math I really like.

So it's a bit of a puzzle, isn't it? You've gotta find the missing digits.

Can you work them out? So it could be a missing hundreds digit, or tens digit, or ones digit.

And you've gotta think really carefully, is it missing from the minuend? Is it missing from the subtrahend? So pause the video and have a go at Task B.

And welcome back.

How did you get on? Did you manage to complete part one? Did you manage to complete part two? Did you get on to part three and find those missing digits? Let's take a look to see whether you got the right answers.

So here are the answers for part one of Task B.

So 555 - 113 = 242.

So very well done if you managed to get the right answers there.

Let's look at part two.

You have to complete each equation using column subtraction.

So that first column subtraction, the calculation you should have done is 463 - 122.

And the difference between those two numbers is 341.

So very well done if you managed to complete that.

And then finally, part three of Task B.

You have to find the missing digits.

A little bit tricky this because you've gotta think really, really carefully.

It shows you really understand column subtraction if you can answer questions like this.

So that first one, the missing ones digit of the subtrahend was a 2.

The missing tens digit of the minuend was a 4.

And the missing hundreds digit of the subtrahend was a 3.

So the calculation should have been 747 - 322 = 425.

So very, very well done if you got onto part three of Task B and you managed to complete that.

And excellent work today in today's lesson, and hopefully you are feeling much more confident about using column subtraction to subtract two dig numbers and three-digit numbers.

Very well done, and hopefully you'll remember how to use it to solve problems in the future.

And let's take a look at our lesson summary.

So start by subtracting the number with the smallest place value.

The minuend appears first in a column subtraction and the subtrahend is written underneath the minuend.

Use zero to show where there are no ones, tens or hundreds represented.