A number line is a pictorial representation of numbers on a straight line. It’s a reference for comparing and ordering numbers. It can be used to represent any real number that includes every whole number and natural number. Just to recollect, the whole number is a set of numbers that include all counting numbers (1, 2, 3,4,5,6 …….) and zero (0), whereas the natural number is the set of all counting numbers i.e. 1, 2, 3, 4, 5, 6……..
Writing numbers on a number line make it easier to compare the numbers. From the above figure, we can see that the integers on the left side are smaller than the integers on the right side. For example, 0 is less than 1, -1 is less than 0, -2 is less than -1, and so on.
Addition on Number Lines:
(i) Adding Positive Numbers
When we add two positive numbers, the result will always be a positive number. Hence, on adding positive numbers direction of movement will always be to the right side.
For example, addition of 1 and 5 (1 + 5 = 6)
Here the first number is 1 and the second number is 5; both are positive. First, locate 1 on the number line. Then move 5 places to the right will give 6.
(ii) Adding Negative Numbers
When we add two negative numbers, the result will always be a negative number. Hence, adding negative numbers direction of movement will always be to the left side.
For example, the addition of -2 and -3
Here, the first number is -2 and the second number is -3; both are negative. Locate -2 on the number line. Then move 3 places to the left will give -5.
Subtraction on Number Line:
(i) Subtracting Positive Numbers
When we subtract two positive numbers, move to the left as far as the value of the second number.
For example, subtract 5 from 2
Here the first number is 2 and the second number is 5; both are positive. First, locate 2 on the number line. Then move 5 places to the left will give -3.
(ii) Subtracting Negative Numbers
When we subtract two negative numbers, move to the right as far as the value of the second number.
For example, subtract -4 from -2
First, locate -2 on the number line. Then move 4 places to the right will give 2.
Step to draw a Number line:
Step 1: Draw a horizontal line with arrows on both ends. (You can also draw a vertical number line)
Step 2: Choose a scale depending on the given number. For example, if you have to plot 5, then you can choose a scale of 1. If you have to plot 50, you can choose a scale of either 5, 10, or 25. (Determining an appropriate scale depends on the factors of the given number)
Step 3: Mark the points at equal intervals. So, if you have chosen 1 as the scale, then mark 0, 1, 2, 3, 4, and so on.
Step 4: Locate the given number. Highlight that point with a circle.
