Category: Free Worksheets Maths: four rules

Subtracting from multiples of 10 in your head by mathsblog.co.uk

Subtracting a 2 digit number from a multiple of 10 can be done ‘in your head’, but it does need care and using an efficient method.

Let’s look at:

50 – 27

Probably the easiest way to do this is by ‘counting on’.

Step 1:  Count on from 27 to the next whole ten (30), which is 3. Hold the three in your head for later.

Step 2: Count on in tens from 30 to 50, which is 20.

Step 3: Add the 20 to the 3 which is 23.

50 – 27 = 23.

(You will often find that children give the answer as 33 rather than 23. That is usually because they have counted on from 20 to 50 which is 30 and then added another 3 to get 33, ignoring the adjustment of the tens.)

Free maths worksheets below:

Subtract from multiples of 10 (p1 and p2)

Another maths worksheet from mathsblog.co.uk which shows the ‘standard’ method for subtraction. It is an excellent practice page at getting used to the method as it only deals with 2-digit numbers. Two points need to be made:

1. It is normally expected that 2-digit subtraction should be done ‘in your head’ and this page is only a beginning to learn the method for harder 3-digit, decimal etc. subtraction later.

2. All the questions here require ‘decomposition’ and there is a danger that a child comes to think that they always have to ‘decompose’ even when it is not necessary.

Standard subtraction of 2-digit numbers (2)

Free maths worksheet from mathsblog.

This is the first maths worksheet on addition using the standard method.

It must be pointed out that usually 2-digit addition should be tackled ‘in your head’. The example on the first page can be done by adding 50 to 76, making 126 and then subtracting 1 making 125. However, to practise the written method it is often useful to keep to smaller numbers so that children gain confidence with the new method

The method is to add the units first, put the units in the answer, and ‘carry’ the ten into the tens column. Then add the tens. A more detailed description of the method to use is on the first page of the worksheets.

Standard written method of addition of two 2-digit numbers (1)

Free maths worksheet from mathsblog.co.uk

Here is another worksheet for subtraction; this time subtracting 9 from 2-digit numbers.

The usual method to do this in your head is to take 10 and then add 1.

So 56 – 9 is done in two steps:

56 – 10 = 46

46 + 1 = 47

56 – 9 = 47

Subtract 9 from a 2-digit number

Free maths worksheet on addition from mathsblog.co.uk

Continuing with our series of simple addition of single digits, here are two maths worksheets on adding 7. The ultimate aim is for children to know, off by heart, the answer to any addition of two single digits. This means that they don’t have to think about it, there is no counting on in their heads, they know it and can answer as quickly as if they were asked what their name is.

adding 7 to a single digit (1)

adding 7 to a single digit (2)

Free subtraction worksheet from mathsblog.co.uk

Here is a maths worksheets concentrating on mental methods of subtracting a single digit from a teen. Much work needs to be done with subtracting from 10 before moving on to this.

There are really two types of question with these which demand different mental approaches.

The first type:  eg  17 – 6 where it is easy to subtract the 6 from the 7 leaving 11. The tens are not affected.

The second type: eg 16 – 8 where the 8 is larger than the 6 is harder.

One method is add on from 8 to 10 (2 which has to be held ‘in your head’) and then count on from 10 to 16 which is easy (6) and add the two together to get 8. It is surprising how often we add on to do a subtraction sum!

A different approach is to know your doubles: knowing double 8 is 16 means the answer has to be 8.

subtract from teen p1

4 times table worksheets from mathsblog.co.uk

The 4 times table is a ‘middle of the road’ table which many children never get a secure recall of. It is, of course, double the two times table and all the answers are even.
Remember the danger is that some children are taught that they only need to count up the answers: 4, 8, 12, 16 etc. However, this is not very helpful if a child needs to know what 4 x 9 is; they do not want to have to go through the whole counting up in fours 9 times to get the answer. The whole idea of tables is that they are learnt, off by heart. To do this it is essential to say them out loud:

4x table worksheets (1 and 2)

Moving towards standard written methods of addition: maths worksheet from mathsblog.co.uk

Just one page is not enough for children to become confident with a method, so I have included here a second maths worksheet which uses the ‘moving towards standard written methods’ of 2-digit addition.
With this method the units are added and placed below the sum, mmaking sure the units are in line and the ten is placed in the tens column. The tens are then added and placed below. The crucial concept here is to remember that it is tens which are being added, so there will be a zero in the units column to ensure that the tens numbers are kept in line. Finally the two answers are added.
This method shows clearly what is happening and avoids the potentially troublesome ‘carrying’ of the tens when using the standard written method.
Moving towards standard written methods of addition (2)