In the number 8.125, what value does the digit ‘5’ have?
4 In the number 4 012 000, what value does the digit ‘4’ have?
5 In the number 12.75, what value does the digit ‘2’ have?
6 In the number 2.09, what value does the digit ‘9’ have?
7 In the number 725.3, what value does the digit ‘3’ have?
8 In the number 7.005, what value does the digit ‘5’ have?
9 In the number 0.13, what value does the digit ‘3’ have?
10 In the number 9.125, what value does the digit ‘5’ have?
2.3 Addition
Most simple additions can be performed mentally, but where many individual numbers have to be added together, like when adding up the fluid intake of a patient over twenty-four hours, the potential for error increases. In these circumstances, it is sensible to perform the calculation on paper.
The numbers are written down in a column format as in the example below. This ensures that the numbers are lined up correctly for the calculation and maintains the place value of each digit within the number. When adding two or more numbers together, the calculation can be performed in any order: 74 + 26 gives the same answer as 26 + 74.
SENSE CHECK
As well as being able to perform calculations, you need to learn ways of checking to make sure you haven’t made a careless mistake. Remember that if you add numbers together, your answer must be greater than the numbers that you started with.
Use the following procedure to check your addition answers:
take one of the numbers that you added up away from the answer
for example, 6 + 9 = 15 and therefore 15 – 9 = 6.
| EXAMPLE 2.1 |
The columns are not usually labelled as hundreds (H), tens (T) or ones (O), but this helps to illustrate the calculation.
Method
The addition is calculated vertically from right to left, starting under the ‘ones’ column and involves three individual calculations, one for the ‘ones’ column, one for the ‘tens’ column and a final calculation for the ‘hundreds’ column.
Process
This gives the answer of 7 hundreds, 7 tens and 8 ones, or 778.
Checking
To check your answer: 778 – 62 = 716.
Not all additions are this straightforward as there will be times when the calculation results in ten or more in a column, such as in Example 2.2.
| EXAMPLE 2.2 |
Method
As before, the addition is calculated vertically from right to left, starting under the ‘ones’ column.
Process
The number ‘12’ is made up of one ‘ten’ and two ‘ones’. Because this column is only used to record the ‘ones’, the two ‘ones’ are recorded here and the ‘ten’ is carried over to the ‘tens’ column. The usual way of doing this is to write a small ‘1’ by the 6 under the ‘tens’ column.
This gives the answer of 7 hundreds, 8 tens and 2 ones, or 782.
Checking
To check your answer: 782 – 69 = 713.
| EXAMPLE 2.3 |
Fluid balance charts are used to monitor the fluid intake and output of patients. You will need to add up fairly large numbers, particularly when monitoring urine output.
If a patient passed 425 millilitres of urine after breakfast and has passed 485 millilitres just before lunch, how much urine have they passed during the morning?
Method
Perform the addition calculation vertically from right to left, starting under the ‘ones’ column.
Process
The number ‘10’ is made up of one ‘ten’ and no ‘ones’. Because this column is only used to record the ‘ones’, a zero is recorded here and the ‘ten’ is carried over to the ‘tens’ column. The usual way of doing this is to write a small ‘1’ by the 8 under the ‘tens’ column.
This part of the calculation is being performed under the tens column, therefore the number ‘11’ is made up of one ‘hundred’ and one ‘ten’ (eleven lots of ten). Because this column is only used to record ‘tens’, a one is recorded here and the hundred is carried over to the ‘hundreds’ column, identified as a small ‘1’ by the 4 under the ‘hundreds’ column.
This gives the answer of 9 hundreds, 1 ten and no ones or 910. So the total amount of urine passed during the morning is 910 millilitres.
Checking
To check your answer 910 – 485 = 425.
TOP TIP
It may seem tiresome adding up large amounts of numbers but persevere and don’t resort to using the calculator on your mobile phone. The NMC standards dictate that Registered Nurses must be able to perform calculations without the use of a calculator.
Self-assessment test 2.2: addition
The recap questions below will help to consolidate your learning about additions. Answers can be found at the end of the book.
1 23 + 77 =
2 156 + 239 =
3 17 + 3294 =
4
