Back to: MATHEMATICS JSS1
Welcome to class!
In today’s class, we will be talking about basic operations. Enjoy the class!
BASIC OPERATIONS
Addition and subtraction of numbers (Emphasis on place values using spike or abacus) Addition and subtraction of numbers (emphasis on the use of number line)
The abacus above, represents the number 374. In the image, we see that:
 We have 3 discs in hundreds’ place
 We have 7 discs in tens’ place
 We have4 discs in ones’ place
Therefore, the place value of 3 is hundred, the place value of 7 is ten and that of 4 is one. To simplify this in mathematical terms, we can write:
3 hundreds + 7 tens + 4 ones
= 300 + 70 + 4
= 374
Now let’s look at a few examples to understand how the spike abacus really helps:

Addition using abacus:
As we can see from the image, 12 is represented as 2 disks in the ones’ place and 1 disk in the tens’ place. Similarly, 25 is 5 disks in the ones’ place and 2 disks in the tens’ place. We know that addition is a combination of numbers. On combining the two numbers, we get 7 disks in the ones’ place and 3 disks in the tens’ place and this can be read as 37.

Subtraction using abacus:
Let’s consider subtracting 12 from 25 in a similar way as shown in the image. In this case we take away the second number from the first, which is the basic definition of subtraction. So we take away 2 discs from 5 and are left with 3 discs. Then we take away 1 disc from 2 to get 1 disc. This number is 13.
Adding and Subtracting Numbers using the Number Line
Adding numbers on a number line is a neat way to see how numbers are added using visual interpretations.
Steps on how to add numbers on the number Line
As indicated in the diagram below:
 To add a positive number means that we move the point to the right of the number line.
 Similarly, to add a negative number implies that we move the point to the left of the number line.
Examples of Adding Numbers on the Number Line
Example:
Simplify by adding the numbers, 2 + 4.
The first step is to locate the first number which is two (2) on the number line.
Adding four (4) means we have to move the point, four (4) units to the right.
In our next class, we will be talking more about Basic Operations. We hope you enjoyed the class.
Should you have any further question, feel free to ask in the comment section below and trust us to respond as soon as possible.
Get more class notes, videos, homework help, exam practice on Android [DOWNLOAD]Get more class notes, videos, homework help, exam practice on iPhone [DOWNLOAD]