Tag: subtraction

Here is a maths worksheet that concentrates on practising subtraction of 3-digit numbers, using the standard, or efficient, written method.

There are several things to look out for when subtracting, including:

a. where each of the three digits on the bottom line are smaller than the 3 digits above them e.g.

987
654

This is the easiest type of question as there is no ‘borrowing’ or ‘adjusting.

b. Where the units are larger on the bottom line e.g.

456
327

Here an adjustment of ten has to be made from the tens column to the units column to carry out the subtraction.

c. Where the tens are larger on the bottom line e.g.

746
395

here an adjustment from the hundreds to the tens has to be made.

d. Where an adjustment from the tens has to be made, but there are no tens and the adjustment has to be made from the hundreds. e.g.

703

445

This is the hardest and one which many children will make a mistake.

For further details of these go to our Four Rules/Subtraction pages.

Subtraction of 3-digit numbers

By the end of year 3 children are expected to be able to subtract a single digit from any 2-digit number. Knowing the patterns involved can make this much easier and this worksheet looks at these patterns.

The number sentence has three missing digits and children are asked to write a digit in each box so that the calculation is correct. There is a limited number of possible correct answers and the second part of the page looks at finding all of them. This is a fairly straightforward page as there is no adjusting or decomposition involved. Look for a logical, well ordered way of working for the second part of the question so that all possible answers are found.

Missing digits in subtraction

 

Last week I published a page of addition with missing digits. This proved very popular and I have had several requests for something similar for subtraction; so here it is.

The calculations have been laid out in the tradition, standard method of written subtraction, except that two of the digits are missing. It is not as easy as it looks to find the missing digits, especially with a question such as:

41? – 2?9 = 207

In this question the units have to be adjusted, which will have a knock on effect in the tens. This page should only be given to children who have quite a good grasp of the standard written method of subtraction, but beware, it is harder than it looks!

Subtraction: missing digits

I have had several requests from people for another page of In Out tables, so here it is. Each table has a set rule. A number goes in, the rule is applied and a number comes out. Straightforward if you are given the number that goes in, but a little harder if you are given the number that comes out. In that case a reverse calculation has to be done.

Some children get into a muddle with these and it is a good idea to point out that if the rule is to add then the OUT number will always be larger than the IN number. If the rule is subtract, then the OUT number will always be smaller than the IN number.

This and lots more worksheets can be found in the Year 5 Calculating category.

In out function machines (2)

Whilst this worksheet appears to be very simple it is surprising how many children get into a bit of a muddle with such activities. A table is shown with a rule for completing it, such as ‘Add 34’. All that has to be done is complete the missing cells of the table following the rule. If the second (OUT) number has to be found then it is a straightforward matter of using the rule. If the first (IN) number has to be found then the rule has to be reversed: it becomes clear as you do the worksheet!

The fourth question does not give the rule, but it can be found by seeing what has happened from the IN number (40) to the OUT number (25); in this case it is subtract 15.

This is well suited to Year 5 children who are good at adding and subtracting two digit numbers mentally. It can be found in our Year 5, Calculating category.

In out function machines (1)

This is the second page of ‘quite hard’ subtraction questions for year 4, which should be answered using mental arithmetic methods, although many adults would struggle to reach the correct answers: they really are quite hard!

Once again it shows that there are several possible ways to approach each question; the key is to choose a method which is efficient and quick. For example, they can all be done by counting on, but this may well not be the quickest way and it is speed and accuracy that we are looking for.

It is also always a really good idea to check answers by carrying out the inverse operation; in this case an addition of the answer and smallest number should give the largest number.

This, and other similar pages can be found in our Year 4 Calculations category as well as in the Four Rules section.

Quite hard mental arithmetic: subtraction_(2)